Physics Learning

TRANSISTOR AS A SWITCH

2010-12-07T13:27:00.005+05:30

DEAR STUDENTS,

PLEASE do this topic for pre board exam .

The transistor always remains in CUTOFF OR SATURATION MODE.In case of silicon the energy gap is 0.6 volt.If the transistor is in cut off mode the collector current is zero.When the input voltage is more than this value the transistor is in active mode & output voltage decreases as the contribution of ICRC INCREASES.tHE OUTPUT voltage decreases linearly till its value is less than about 1volt.After this the change becomes non linear & transistor goes to saturation mode.SO low input means OFF & HIGH INPUT MEANS ON.(REFER TO N.C.E.R.T PAGE 496)

ROTATIONAL MOTION ASSIGNMENT

2010-11-20T11:05:00.004+05:30

Assignment of rotational motion (class 11)

Q.1 Why is the speed of whirl wind in a tornado alarmingly high?
(Use L = Iw)

Q.2 If Earth was to shrink suddenly to half its radius, what will happen to the length of the day?
(Use I=2/5Mr^2 and L=Iw)
Ans. Decreases

Q.3 When there is no external torque on the rotating body which of the following questions can change:-
1) Angular acc
2) Angular momentum
3) Angular Speed

Q.4 Equal torques are applied on a cylinder and a hollow sphere. Both have the same mass and radius. The cylinder rotates about its axis and the sphere about one of its diameters . which will acquire greater speed.
Torque=I*angular acc. Angular acc= torqe/I
Q.5 Asolid sphere is made to roll down from the same ht. on two inclined planes having having theta 2>theta 1. in which case will it take less time to reach the bottom?
Ans. In case of theta 2.

Q.6 The moment of inertia of 2 rotating bodies A&B are Ia & Ib (Ia>Ib)
And their angular momenta are equal. Which has greater k.i.?
Ans. B

Q.7 If the polar ice caps melts, how will it affect the duration of the day?
L=Iw=const.
Ans. L.w=2pie/T therefore, length of the day will increase.

resistance and resistivity

2010-08-07T20:20:00.002+05:30

hey students this video is about resistance, resistors and resistivity

electricity and magnetism

2010-08-07T20:10:00.002+05:30

hey students i am going to upload a awesome video on electricity and magnetism

electricity and magnetism

2010-08-07T19:58:00.002+05:30

hey students i am going to post an awesome video on electricity and magnetism

electricity and magnetism

2010-08-07T19:47:00.002+05:30

hey students i am going to give all of you a awesome video on electricity and magnetism

basic principles and working of cyclotron

2010-08-07T19:18:00.002+05:30

hey student basic s ,i am going to post a beautiful video aboutprinciples and working of cyclotron

magnetic effects of current

2009-12-10T09:35:00.002+05:30

DEAR STUDENTS OF CLASS 10
Here is an assignment based on comprehensive contMagnetic Effects of Current

Life skills

1.To illustrate the use of MAGNETISM in medicine a visit to a diagnostic centre where MRI (MAGNETIC RESONANCE IMAGING )
.is done. The students will meet the RADIOLOGIST to find
(a) the technology used in doing MRI
(b) The kind of organs in which MR imaging of the body is performed.

2.To visit the site where ALTERNATING CURRENT is generated & is sent through TRANSMISSION LINES. The ill effects of ELECTROMAGNETIC RADIATION associated with changing A.C.can be understood.

ACTIVITY BASED FORMATIVE ASSESSMENT

Activity 1
The wire AB is carrying current in downward direction as shown:-

A

A

A compass needle is first placed at pt.A & is taken to pt.B
Q1.What change in deflection is observed as the distance of compass needle is increased
From the wire.
Q2.For same position of compass needle the current in the wire is doubled. What change in the deflection is observed now?

Activity 2

Q1.A rod is carrying current in downward direction as shown in the diagram. It is placed in the uniform magnetic field as shown:

Answer the following questions
a) Give the direction of force experience by the rod.
b) State the rule which helps introducing the direction of force
c) How will the displacement of rod affected if the (i) Current in the rod is increased
(ii) Magnitude of magnetic field is
increased.
Q2. A selected shown in the diagram given below carries current as shown:

Mark the polarity at 2 ends.
Mark the region inside the solenoid where the field is uniform.
Complete the pattern.

Q3.In the diagram given below mark the arrows and complete the pattern (to depict the magnetic lines of force) Given the coil is perpendicular to plane of paper (a) what is the nature of magnetic field near the centre?
b) Which rule helps in drawing the direction of magnetic field lines?

Q4.In the diagram given below a coil is connected to a Galvanometer as shown:
A magnet is taken towards/ away from the coil explain the following observations:-

There is no deflection in the (G) when the magnet is stationary

The direction of deflection becomes opposite when the particular pole of the magnet is taken away instead of taken towards the coil.
Faster the motion greater is the deflection.

Match the following (For domestic electric in circuits

Or
Fill in the Blanks

Colour of Earth wire____________________Green

Colour of Neutral wire ____________________Black

Colour of live wire _____________________red

Two ratings of fire wire ____________5A, 15A

Connection to Earth provides a __________________lower resistance path

OR
Match the following

Earth Wire black

Neutral wire 5A, 15A

Electric rating green

livewire Geyser,airconditioner

Higher power rating appliances red
Lower power rating Healing effect of current

The fuse melts due to electric bulb, fan, electric ion

communication

2009-12-03T12:57:00.006+05:30

Dear students

I want you to revise the following questions on communicationPHYSICS QUESTIONS

# Short answer type-

What are the three basic units of a communication system?
Ans- (i) Transmitter (ii) Communication channel
(iii) Receiver

Identify the parts X and Y in the following block diagram of a generalized communication system-
Ans- Part X is information source and Y is information channel/medium

What is the function of a transmitter antenna ?
Ans- To radiate power fed from transmitter into free space.

How does the effective power radiated by an antenna vary with wavelength ?
Ans- Power radiated by an antenna is inversely proportional to the square of the wavelength of the carrier wave.

What is the meaning of the term “attenuation” in communication system ?
Ans- Attenuation is the loss of strength of a signal while propagating through the medium.

Name three common types of wave propagation in space communication ?
Ans- (i) Ground wave (ii) Space waves or line of sight method
(iii) Sky waves

7. Why is ground wave transmission of signals restricted to a maximum frequency of 1500 kHz?
Ans- In ground wave propagation, attention increases with increase in frequency. For frequencies
above 1500 kHz the loss of power becomes extremely large. Hence, for ground wave
propagation, the upper frequency limit is 1500 kHz.

Define modulation index as referred to AM .
Ans- the modulation index of an AM wave is defined as ratio of the amplitudes of the modulating
Signal and the carrier wave.

What is the composition of amplitude modulated signal wave ?
Ans- The modulated signal consists of the carrier wave of angular frequency and side waves of angular frequencies.

What is Band pass filter ?
Ans- A band pass filter allows a band of frequencies to pass through and reject frequencies higher/lower than that band.

( SHORT ANSWER TYPE QUESTION- 2marks )

What is a communication system ? Draw a neat block diagram of a communication system.
What do you mean by point-to-point communication and broadcast ? Give examples too.
Write main advantages and disadvantages of AM technique.
Briefly explain why do we need a much higher bandwidth for a digital signal transmission than an analog signal.

( LONG ANSWER TYPE QUESTION )

1. Analytically explain the process of amplitude modulation. What is the frequency spectrum of AM signal ?
2. What is demodulation ? With the help of a circuit diagram explain the principle of a demodulator.
3. A TV tower has a height ‘h’. Derive the expression the maximum distance up to which signals can be received on earth.
4. A schematic arrangement for transmitting a message signal (20Hz to 20kHz) is given below-

n.Give two drawbacks from which this arrangement suffers. Describe briefly with the help of a block diagram the alternative arrangement for the transmission and reception of message signal.

project based learning

2009-11-19T10:56:00.002+05:30

Dear students,
I wish you to see this power point presentation to see the effectiveness of PBL.
Project-based learning (PBL): best defined as instruction relating questions and technology relative to the student’s everyday lives to classroom projects. Students form their own investigation of their own group which allows students to develop valuable research skills. The students engage in design, problem solving, decision making, and investigative activities. It allows students to work in groups or by themselves and allows them to come up with ideas and realistic solutions or presentations. Students take a problem and apply it to a real life situation with these projects.

2009-03-10T21:48:00.000+05:30

Q1. An electron alphaparticle,aproton have same kinetic energy.which one of these has the largest de-Broglie wavelength?
Q2. Why should the material used for making permanent magnets have high coercivity?
Q3.Distinguish between sinusoidal &pulse signal.
Q4 .In n-type silicon name the type of minority carriers &write the type of dopants.

Q5.Why is frequency modulation preffered over amplitude modulation for transmission of music.

Let us do something interesting

2009-03-10T12:44:00.001+05:30

Dear students'Iwsh to give u one mark questions recently asked in board exams_

Q1. Unpolarised light is incident on a plane surface of glass of refractive index(mu) at an angle .If the reflected light gets totally polarised,write the relation between i & (mu)

Q2.Two nuclei have mass no. in the ratio1:3.What is the ratio of their nuclear density.

Q3.Draw a diagram to show refraction of a plane wavefront incident on a convex lens & hence draw refracted wavefront.

Q4.Magnetic lines can be entirely cofined with in the core of a Toroid ,but not with in a straight solenoid.why?

2009-02-26T22:45:00.000+05:30

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FUNDAS OF ELECTROSTATICS

2009-02-25T09:09:00.000+05:30

Questions on MAGNETIC EFFECTS OF CURRENT& MAGNETISM

2008-12-01T09:54:00.000+05:30

Dear students
I am giving you important questions on MAGNETIC EFFECTS OF CURRENTS & MAGNETISM for rivison work.Class XII
Physics
Magnetic Effects of Current

. 1. A 0.5m long solenoid has 500 turns and has a flux density of 2.52 x 10-3 T at its centre. Find the current
in the solenoid.
2. A charged particle is moving in a perpendicular magnetic field. Derive the equation of path of charged
particle.
3. Give the construction, theory and working of a moving coil galvanometer.
4. The electron in the hydrogen atom circles round the proton with speed of 2.18 x 106 m/s in an orbit of
radius 5 x 10-10 m. What magnetic field does it produce at the proton?
5. A flat circular coil of 50 turns of max radius 25cms is in a fixed vertical place and has a current of 2A flowing through it. A small coil of 1cm2 area and having 100turns, is suspended at the centre of the circular coil in a vertical plane at an angel of 300 to that of the large coil. Calculate the torque that will act on small coil, when it carries that of the large coil. Calculate the torque that will act on small coil, when it carries a current of 1m A. What is the mutual inductance of the two coi
6. Find the value of resistance required to convert 0-5 m A into a voltmeter reading 0-10V. Resistance of
the millimeter is 2.5 ohms
7. Obtain an expression for the magnetic field at the centre of a square ofside 2a, carrying current I.
8. Derive an expression for the torque acting on a current carrying rectangular loop of wire placed in a
uniform magnetic field.
9. The protons are accelerated by a cyclotron, when a field of 2 wb m2 is
applied perpendicular to the plane of Dee. Calculate the energy of protons in Mev, if the circular part of
the protons has a radius of 0.4m before they leave the cyclotron.
1. Obtain expression for the magnetic field at the axial and equatorial point in case of a bar magnet. What are
neutral points?
2. Two iron bars are identical in appearance, one is a magnet and the other is not. How do you know which iswhich? You are not permitted to suspend the bars or use any other apparatus.
3. We find that more low energy cosmic rays reach the earth at the magnetic poles than at the magnetic equator? What could be the reason for this?
4. A 15 kV electron beam moving horizontally is subjected to horizontal magnetic field of 0.4 G normal to its initial direction. Estimate the radius of curvature of the path and up and down deflection of the beam over a distance of 0.3m.
5. Derive an expression for the torque acting on a magnetic dipole placed in a uniform magnetic field and hence define the magnetic moment of a dipole. Give the units of magnetic dipole.
6. Discuss the magnetism due to earth, which can be the possible cause of earth’s magnetism? Explain how the knowledge of elements of earth’s magnetism determines earth’s magnetic field completely.
7.. A neutral point is found on the prolongation of the axis of a bar magnet at a distance be 10cms from on end. If the length of the magnet be 10 cms and BH=0.3 G find the magnetic moment of the magnet.
8.Define coercivity and retentivity. How are soft iron and hard steel distinguished by the value of these quantities? Sketch the hysterisis loop for soft iron and hard steel. What do you infer about these materials from their hysterisis loops?
9.Write the relation for force between two parallel wires carrying current and hence define unit of current. 10. Find the flux density of the magnetic field to cause 62.5ev electron to move in a circular path of radius in 5cm given m = 9.1 x 10-31 kg, e = 1.6 x 10-19C.
11. Calculate the torque on a 50 turn circular look of radius 10cm, when placed with its place at 600 with a
magnetic field of 3.1 x 10-5T. The current through the coil is 2A.
12. To increase the current sensitivity of a moving coil galavanometer by 50%, its resistance is increased so that its new resistance becomes twice its initial resistance. By what factor does its voltage sensitivity change. 13.State Biot-Savart’s law. Using this law, obtain an expression for the magnetic field at a point situated on axis of a current carrying circular coil.

14.Two very long parallel wires A & B carry currents of 10A and 2A respectively and are at a distance of 20cm from each other. A third wire C of length 15cm and carrying a current of 10A is placed mid way between them. What is the magnitude and direction of force on wire C? The direction of current in all the three wire is the same

15. A long straight wire carries a current of 50A. An electron moving at 107m/sec is 5cm from the wire. Find the force acting on the electron if velocity is directed (i) towards the wire (2) parallel to the wire (iii) perpendicular to the directions defined by (i) and (ii)
16. Using Biot Savart LawFind an expression for the magnetic field due to straight current carrying conductor.

VIVA VOCE ON PRACTICAL CLASS12

2008-11-25T10:40:00.000+05:30

Dear students,
I am giving you questions based on practicals class12
Test Based on Viva
Class XII

1. Define spherical aberration and draw diagram to show it in case of concave mirror.
2. What is parallax? How is it removed?
3. Define dispersion of light. Give its cause.
4. Show dispersion of white light into seven colours.
5. Define lateral displacements and give the factor on which it depends.
6. Define critical angle and deduce the relation between refractive index and critical angle.
7. Explain U-V graph in case of image formation in a convex lens.
8. Distinguish between primary and secondary cell. (give two differences)
9. How does rheostat act as a variable resistor, potential divider? (draw a diagram)
10. What a non inductive coil? Give one special feature of non inductive coil?
11. Draw neat and label diagram of leclanche cell.
12. Write chemical equation in Daniel cell.
13. Why is the emf of auxiliary battery greater than the emf to be measured?
14. Why are standard resistances made up of constantan and Manganin?
15. Define figure of merit and give it is S.I unit.

-------------------------------------------------------------------------------------------------------------------------------
Test Based on Viva
Class XII

1. Define spherical aberration and draw diagram to show it in case of concave mirror.
2. What is parallax? How is it removed?
3. Define dispersion of light. Give its cause.
4. Show dispersion of white light into seven colours.
5. Define lateral displacements and give the factor on which it depends.
6. Define critical angle and deduce the relation between refractive index and critical angle.
7. Explain U-V graph in case of image formation in a convex lens.
8. Distinguish between primary and secondary cell. (give two differences)
9. How does rheostat act as a variable resistor, potential divider? (draw a diagram)
10. What a non inductive coil? Give one special feature of non inductive coil?
11. Draw neat and label diagram of leclanche cell.
12. Write chemical equation in Daniel cell.
13. Why is the emf of auxiliary battery greater than the emf to be measured?
14. Why are standard resistances made up of constantan and Manganin?
15. Define figure of merit and give it is S.I unit.

moving charges&magnetism

2008-11-19T09:42:00.000+05:30

Dear students I have made an impressive lesson on moving charges & magnetism.You can collcct
the CD of this lesson from senior physics lab.

2008-09-19T22:06:00.002+05:30

2008-09-19T22:06:00.001+05:30

to find equivalent capacity of the networks given below

2008-09-19T22:06:00.000+05:30

Dear students

Find the eq. capacity of networks given and submit the answer-

MANAGING ELECTRONIC WASTE

2008-07-16T22:24:00.000+05:30

It is very interesting to note that in INDIA Electronic goods,Mobilephones,from Kabadiwallah are sold to scrap dealers.The local scrap dealer takes apart crude components & after Acid-Washiong metals like Gold, Silver ,Copper ,Steel ,Brass and Platinum are recovered. Ordinary Jewellers then buy expensive metals like Gold and Silver. It is high time that GOVT. should do some thing in this direction.

THE INVISIBLE THREAT

2008-07-13T22:52:00.000+05:30

We cannot live without the items such as CELLPHONE;TOASTER;HAIRDRYER;VACCUM CLEANER etc.Dr RAMANANDA NADIG president health care global triesta sciences BANGALORE has declared that these gadgets emit EM radiation. It is believed that sustained exposure to 2 milliGauss increases the risk of brain cancer.

electric field

2007-12-28T21:54:00.000+05:30

http://freemindshare.com/file/djvy46OUVX/

properties of electric charge

2007-12-10T11:11:00.003+05:30

http://www.freemindshare.com/file/lz23MOUWXY/

Mind Maps for learning

2007-11-30T11:10:00.000+05:30

click on the following links for viewing mindmaps(factmaps) on various physics topics.
1 wavefront
http://freemindshare.com/map/m46BHKQVWX/

2. Amplifier
http://freemindshare.com/map/bdgnuwz3NX/

3.Oscillator
http://www.freemindshare.com/map/bcepty1268/

4. Various Methods of Electron Emision
http://www.freemindshare.com/map/279CEGPRWY/

assignment rayoptics

2007-08-31T22:24:00.000+05:30

Ray Optics Assignment
Class XII

1. State the principle of reversibility of light.
2. A straight rod appears bent in water. Why?
3. A microscope is focussed on a dot at the bottom of a beaker. Some oil is
poured into the beaker to a height of y cm and it is found necessary
to raise the microscope through a vertical distance of x cm to bring the dot
again into focus. Express refractive index of oil in terms of x and y.
4. The sun near the horizon appears flattened at sunset and sunrise. Why?
5. A ray of light while travelling from a denser to a rarer medium undergoes
total reflection. Derive the expression for the critical angle in the terms
of the speed of light in the respective media.
6. What is total internal reflection? Under what conditions does it take place?
7. In fig. Shows a triangular prism of glass. A ray incident normal on one
face is totally reflected. What can you conclude about the minimum
value of index of refraction of glass?
. A light ray travels from medium 1 of refractive index m1 to medium 2 of
refractive index m1 to medium 2 of refractive index m2, where m1 an expression for critical angle of incidence.
9. Explain with the help of diagram, how optical fibres transmit signals.
10. Mention some important applications of optical fibres.
11. State the advantages of totally reflecting prisms over plane mirrors.
12. A convex lens made up of a material of refractive index m1 is immersed in a
medium of refractive index m2. Trace the path of a parallel beam of light
passing through the lens when (I) m1=m2 (ii) m1 concave lens of a material of refractive index m is immersed in a medium of
refractive index m/ . When a parallel beam of light is incident on the lens,
trace the path of the emergent rays (if) m/ >m (ii) m/ = m and (iii) m/ < m.
13. A convex lens (mg = 1.5) behaves as a converging lens when dipped in water
(mw=1.33) whereas it behaves as a diverging lens when dipped
in carbon disulphide (mc=1.65). Why?
14. Write expressions for the equivalent focal length and equivalent power when two thin lenses are (a) in contact (b) separated by distance d.

15. In the figure shows a plano convex lens with its plane surface silvered. Calculate its focal length.

16. In the figure shows and planoconvex lens with its convex surface silvered. Calculate its focal length.

17. Explain why light is dispersed when passing through a prism.
18. Refractive index of glass for violet, yellow and red colours are mv, my and
mr respectively. Write these in decreasing order of value. Justify your
answer.
19. Define angular dispersion and dispersive power. Express them mathematically.
20. Define the term angular dispersion. Draw the path a ray of white light
passing through a prism and mark angular dispersion on it.
21. With the help of a ray diagram, indicate the path of red and violet rays
form a beam of composite light passing through a prism.
(i) .22. Distinguish between magnifying power and resolving power of a
microscope.
23. Define the terms magnifying power and resolving power of a telescope.
24. Draw a labelled diagram of an astronomical telescope forming the final image
at the near point. Write down the formula for its magnifying power.
25. Show, by drawing a labelled diagram, the image formation in a compound
microscope.

Assignment-wave optics

2007-08-29T10:46:00.000+05:30

Wave Optics

1. Name the scientist who first proposed the wave theory of light.
2. Name the phenomenon which confirm the wave nature of light.
3. What is a wave front?
4. Define a ray of light.
5. How is the direction of a ray related to a wave front?
6. What is the phase difference between two points on a wave front?
7. How much is the phase difference corresponding to path difference of l two waves reaching a point?
8. What is the shape of wave front from a point source?
9. What is the shape of wave front of a line source of light?
10. Which type of wave front corresponds to a parallel beam of light?
11. A small piece of stone is dropped into a pond of still water. What is the shape of wave front?
12. A spherical wave front is increasing in size. Whether the rays constitute a convergent or a divergent beam?
13. Rays of light are converging to a point. Is the radius of the spherical wave front increasing or decreasing in size?
14. What is the shape of the wave front of light emerging out of a convex lens when a point source is placed at its focus?
15. Is it necessary that the amplitude be constant over a given wave front?
16. Can two wave-fronts cross one another? Give reason.
17. What is the geometrical shape of a portion of a wave front of light from a distant star intercepted by the earth?
18. What will be the shape of wave front of light coming from a point source place at infinity?
19. Which principle is used to find the position of a wave front after some time?
20. What are secondary wavelets?
21. State Huyghen’s principle.
22. Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?
23. A light wave enters from air into glass. How will the following be affected:
i) Energy of the wave
ii) Frequency of the wave?

24. When a wave undergoes reflection at a denser medium, what happens to its phase?
25. If a wave undergoes refraction, what will be the phase change?
26. When monochromatic light is incident on a surface separating two media, the reflected and refracted light both have the same frequency as the incident frequency? Explain why?
27. When light travels from a rarer to a denser medium, it loses some speed. Does the reduction in speed imply a reduction in the energy carried by the light waves?
28. In the wave picture of light, intensity of a light is determined by the square of amplitude of wave. What determines the intensity of light in the photon picture of light?
29. A narrow pulse of light is sent through a medium, will you expect the pulse to retain its shape, as it travels through the medium?
30. The speed of light in still water is c/m, where m is refractive index of water. What is the speed of light in a stream of water flowing at a steady speed of v relative to observer?
31. A and B are two points on a water surface where waves are generated. What is the phase difference if (a) A and B are on the same wave front but separated in distance by the wavelength l (b) If A and B are on successive crests, but linearly separated by the distance 2.5l and (c) A and B are on successive troughs?
32. State the principle of superposition of waves.
33. What is interference of waves?
34. What is the main condition to produce interference of light?
35. What are coherent sources of light?
36. State the conditions which must be satisfied for two light sources to be coherent.
37. Can two independent sources of light be coherent?
38. Can interference fringes be produced by using tow identical bulbs?
39. Give a relation between path difference and wave length for constructive interference between two waves.
40. State the path difference between two waves for destructive interference.
41. What is the effect on the interference fringes if the separation between the two slits in Young’s double slit experiment is increased?
42. What is the effect on the interference fringes in a Young’s double slit experiment if the screen is moved away from the plane of the slits?
43. What will be the effect on the interference fringes in Young’s double slit experiment, if the monochromatic source is replaced by another monochromatic source of shorter wave length?
44. Why should we have a narrow source to produce good interference fringes?
45. How can the fringe width be increased in Young’s double slit experiment?
46. What is the shape of interference fringes in Young’s double slit experiment?
47. Is the central fringe bright or dark in Young’s double slit experiment?
48. How much is the distance in terms of fringe width b between central bright and fourth dark fringe?
49. In Young’s double slit experiment if the distance between two slits is halved and distance between the slits and the screen is doubled, then what will be the effect on fringe width?
50. Can we observe interference maxima on the screen if the two slits are separated by less than a wave length of light used?
51. No interference pattern not detected, when the two interference sources are infinitely close to one another. Why?
52. Why is interference pattern not detected, when the two interference sources are fat apart?
53. Light from two coherent sources is reaching a point where path difference for yellow light is 3l/2. What will be the colour of the fringe at this point?
54. What is the ratio of the fringe width for bright and dark fringes in Young’s double slit experiment?
55. Does interference phenomenon violate the law of conservation of energy?
56. Does interference phenomenon reveal the nature of light waves?
57. What is effect on interference fringes in Young’s double slit experiment if one slit is covered?
58. In Young’s double slit experiment, lights of green, yellow and orange colours are successively used. Write the fringe widths for the three colours in increasing order.
59. In Young’s double slit experiment, each source has intensity I0. What is the intensity at the point of constructive interference?
60. One of the two slits in Young’s double slit experiment is so painted that it transmits half the intensity of the other. What is the effect on interference fringes?
61. What happens to the interference pattern if the phase difference between the two sources varies continuously?
62. Why is a slight shaking of the picture on a television screen noticed when a low-lying aircraft passes overhead?
63. Two slits in Young’s double slit experiment have widths in the ratio 81:1. What is the ratio of the amplitudes of light waves from them?
64. What is the ratio of the slit width when amplitudes of light waves form then have a ratio Ö2:1?
65. Two waves of amplitudes 3m and 2 m reach a point in the same phase what is the resultant amplitude?
66. Two waves of amplitude 3mm and 5mm reach a point in opposite phases. What is the resultant amplitude?
67. The phase difference between two waves reaching a point in p/2. What is the resultant amplitude if the individual amplitudes are 3mm and 4mm?
68. In Young’s double slit experiment, two disturbances arriving a point P have a phase difference of p/3. What is the intensity at this point P have a fraction of maximum intensity I0?
69. Two coherent sources emit waves of amplitudes a and 2a. They meet at point P equidistant from the two sources. If the intensity of the first is I, what is the resultant intensity at point P?
70. Consider the interference between two sources of intensities I an 4I. Obtain the intensity at a point where the phase difference is (I) p/2 (ii) p
71. In Young’s double slit experiment, the intensity of central maximum is I. What will be the intensity at the same place if one slit is closed?
72. What happens to the light energy when light waves interfere destructively at a point?
73. What will be the effect on the fringes formed in Young’s double slit experiment, if the apparatus is immersed in water?
74. Why is it comparatively difficult to observe interference in light waves as compared to that in water waves?
75. Two slits in Young’s double slit experiment are illuminated by two different sodium lamps emitting light of same wavelength l. Do you observe any interference pattern on the screen?
76. Give the shape of the fringes observed in the Lloyd’s mirror experiment.
77. Is there any difference between the colours emerging from a prism and the colours of a soap film seen in sunlight?
78. Thin films, such as a layer of oil on water, show beautiful colours when illuminated by white light. Name the phenomenon involved.
79. Why does a soap bubble show beautiful colours when illuminated by white light?
80. Why does the colour of the oil film on the surface of water continuously change?
81. Why does an excessively thin film appear black in reflected light?
82. Why do thick films not show interference effects?
83. An observer sees a green fringe passing through a given point in an oil film. Would other observer looking at the same point necessarily see green fringe there? Explain by writing down the necessary relation.
84. What type of fringes are seen in an air wedge
85. Give the shape of the fringes observed from a thin air film formed by placing a convex lens on top of flat glass plate (Newton’s arrangement)
86. Is the central fringe bright or dark in Lloy’s single mirror method? Give reason.
87. What is diffraction of light?
88. What is the cause of diffraction?
89. What should be the approximate slit size to observe diffraction with it?
90. What should of ht order of size of obstacle or aperture for diffraction of light?
91. Is it correct to say that diffraction is interference between different parts of the same wave front?
92. A small circular disc is placed in the path of light from a distant source. Will the centre of shadow be bright or dark.
93. What is the condition for first minimum in case of diffraction due to single slit?
94. In what way is diffraction from each slit related to the interference pattern in Young’s double slit experiment?
95. In a single slit diffraction experiments, the width of the slit it made double the original width. How does this affect the size and intensity of the central diffraction band?
96. Why do we fail to observe the diffraction from a wide slit illuminated by monochromatic light?
97. Coloured spectrum is seen, when we look through a Muslim cloth. Why?
98. Why can sound waves be diffracted more easily than light waves?
99. Two students are separated by a 7m partition wall in a room 10m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other, even though they can converse easily?
100. Rdiowaves diffract pronounced around the buildings, while light waves, which are e.m. waves, do not. Why?
101. If light bends around obstacles, then why can’t we see around a building?
102. You are able to hear a person standing behind a wall but not see him, though both light and sound are waves. Why?
103. A single slit diffraction pattern in completely immersed in water without changing any other parameter. How is the width of central maximum affected?
104. Why are diffraction effects more prominent through a slit formed by two blades than through a slit formed by two fringes?
105. Geometrical optics is based on the assumption that light travels in a straight line. Diffraction effects disprove this assumption. Yet the geometrical optics assumption is so commonly used in understanding location and several other properties of images optical instruments. What is the justification?
106. What is Fresnel’s distance?
107. Name one such phenomenon that is shown by light waves but not by sound waves.
108. Which phenomenon leads us to conclude that light has transverse wave nature?
109. What do you mean by polarisation waves?
110. Why longitudinal waves cannot be polarised?
111. Light waves can be polarised while sound waves cannot. Why?
112. What information one does obtain from polarisation about the nature of light?
113. What is plane polarised light?
114. Define circularly polarised light.
115. Define elliptically polarised light.
116. Is light from a sodium lamp plane polarised?
117. Can e.m. waves be polarised?
118. Can you recognise with the naked eye whether the given light is polarised or not?
119. Is the blue light from the sky polarised or not?
120. Which field vector, electric or magnetic, is used to represent the polarisation of an e.m. wave?
121. Why does the electric field of e.m. wave determine the state of polarisation and not its magnetic field?
122. Sun glasses are made of polaroids and not of coloured glasses. Why?
123. Give two example of commonly used devices which make use of polaroids.
124. Which among X-rays, sound waves and radiowaves can be polarised?
125. A beam of light is incident on a polaroid. On rotating the polaroid through 3600 about the incident ray as the axis, the intensity ray as the axis, the intensity of transmitted light varies between a maximum and a non-zero minimum. What can you say about the state of polarisation of the incident light?
126. State Malus law.
127. State Brewster law.
128. Define polarising angle of incidence.
129. What is the angle between reflected and transmitted rays at the polarising angle of incidence?
130. Does the value of polarising angle depend on the colour of light?
131. A ray of light falls on a transparent slab of refractive index 1.732. IF reflected and refracted rays are mutually perpendicular, what is the angle of incidence?
132. A polariser and analyser are so oriented that no light is transmitted. What is the angle between the axes of polariser and analyser?
133. A polariser and analyser are so oriented that intensity of transmitted light is maximum. If the analyser is rotated through 600 , what fraction of the maximum light is transmitted?
134. What percentage of the incident light is transmitted if the angle between polariser and analyser is 300 ?
135. Write two simple uses of polaroids.

First Hotel Planned in Space

2007-08-13T21:51:00.000+05:30

GALACTIC SUITE -FIRST HOTEL PLANNED IN SPACE
A BARCELONA based architect says that the first space hotel,300 miles in orbit will be the most expensive one in the galaxy.can you imagine the cost of three day stay in space is $4 million.The reservations will begin in 2008.The first hotel in space will orbit earth every 80 minutes.

MISSION ON MARS

2007-08-10T22:01:00.000+05:30

NASAS ROBOTIC phoenix mars lander blasted off for the red planet on 5.8.07.It will hopefully resolve whether or not our neighbouring planet has ever played host to microbial world.The space probe will land on the planets arctic plains next year to begin an exhaustive search for organic compounds.This study will give the scientists an insight into probability of manned mars missions.

PASSION QUOTIENT

2007-08-10T19:30:00.000+05:30

Passion is more importantSubmitted by manjukapoor on Fri, 2007-08-03 03:27. -->GENERAL
Passion Quotient is as important as IQ
Ever wanted to know about your passion quotient (PQ)? Well, if not, go for it as even a 20 percent increase in PQ can act like virtual energy and work wonders for students and professionals alike. “IQ or intelligence quotient comes more like a hard-wired DNAQ bonanza which you cannot really improve upon, whereas you can raise your PQ threshold and become more creative by making some conscious efforts”, author Virender Kapoor writes in The Greatest Secret of Success: Your Passion Quotient. HE says people with high IQ but low passion and drive have rarely made it to the top.” The fire in the belly, that is passion, contributed more to Albert Einstein’s success than his high IQ. Human emotions cannot be measured accurately; PQ cannot be assigned a number or figure as in the case of IQ. “But PQ is notional, indicative and representative in nature. “Kapoor also relates passion with creativity and creativity needs passion. Passion can fire up that creative genius which all of us to some degree possess.” Passion becomes the propelling force for professionals, entrepreneurs, musicians, actors, lawyers, pilots, writers, scientists, fashion designers and almost every conceivable human profession. It gets linked directly to the inner motivation, which is a guiding spirit for self-motivated successful people.

Assignment 1

2007-07-25T09:49:00.001+05:30

Dear Students,

Following are some special circuits. Find the equivalent resistance for each of them in ohm.

Global Warming

2007-07-25T09:40:00.001+05:30

Albert Einstein

2007-07-13T10:53:00.001+05:30

Sunita Williams

2007-07-07T12:27:00.001+05:30

Facts about Electrostatics

2007-05-28T21:45:00.000+05:30

The simple apparatus that can detect the presence of electric charge is aGOLDLEAFELECTROSCOPE.
The electric field due to a point charge is spherically symmetric as the magnitude of electric field at any point on sphere drawn around a charge with pt. charge at centre is same.
The electric field due io a dipole is cylinderically symmetric.
A metal sphere of radius 1cm. cannot hold a charge of 1coulomb.