1. Answer, in brief, any four questions. 4x2=8

a) A large number of free electrons are present in metals. Why is there

no current in the absence of electric field across it ?

b) Draw a circuit diagram of Wheatstone bridge. What is the balanced

condition of it ?

c) How will the magnetic field intensity at the centre of a circular coil

carrying current change, if the current through the coil is doubled and

the radius of the coil is halved ?

d) Why do two straight conductors carrying current in opposite direction

repel each other ?

e) What is self inductance of a coil ? Write two factors on which it depends.

f) For a direct current supply a capacitor containing circuit becomes an

open circuit. Explain.

2. Answer, in brief, any four questions. 4x2=8

a) A hydrogen atom is stable in the ground state. Why ?

b) Draw a circuit diagram for p-n junction diode in forward bias. Sketch

the voltage versus current graph for it.

c) How does a daughter nucleus differ from its parent nucleus when it

emits an -particle ?

d) Why is the mass of nucleus slightly less than the sum of mass of

constituent nucleons ?

e) Discuss ozone layer depletion.

f) State Hubble's law and write the significance of Hubble's constant.

3. Answer, in brief, any one question. 2

a) Sound waves are also called pressure waves. Why ?

b) What is a progressive wave ? Write its representative wave equation.

4. Answer, in brief, any one question. 2

a) State and explain Huygen's principle.

b) What is a polarizing angle ? Does it depend on the wave length of light ?

Group 'B'

5. Answer any three questions. 3x4=12

a) State and explain principle of potentiometer. Explain with the help of

circuit diagram, the use of potentiometer for determination of internal

resistance of a cell.

b) What is thermoelectric effect ? How does the thermo emf of a

thermocouple vary with increase in temperature of hot junction, keeping

the cold junction at 0o

C ? Explain.

c) What are the magnetic elements of the earth ? Prove the relation

cot2 cot21

+cot2

where is the true dip and 1

and 2 are the

apparent dips.

d) Derive expressions for the impedance and phase angle of an alternating

current circuit with an inductor L, a capacitor C and a resister R in

series.

6. Answer any three questions. 3x4=12

a) Describe the construction and working of a He-Ne laser.

b) What is Zener effect ? Explain the use of Zener diode as a voltage

regulator.

c) State laws of radioactive disintegration. Hence, obtain decay law and

define disintegration constant.

d) Describe the environmental implications of the following energy sources.

i) fossil fuels and ii) nuclear fuels.

7. Answer any one question. 4

a) Define resonance. Describe an experiment to determine the velocity

of sound in air and end correction of the tube by resonance method.

b) What are beats ? Prove that the beat frequency is equal the difference

of frequences of two superposing waves.

8. Answer any one question. 4

a) Describe Michelson's method for the determination of speed of light.

b) What are coherent sources of light ? Show that in Young's double slit

experiment, the dark and bright fringes are equally spaced.

9. Answer any two numerical questions. 2x4=8

a) The resistance of a conductor at 20oC is 3.15 and at 100oC is 3.75.

Determine the temperature coefficient of the conductor and resistance

of the conductor at 0oC.

b) An electron is moving at 106m/s in a direction parallel to an infinitely

long straight wire carrying a current of 5A and separated by a

perpendicular distance of 10cm in air. Calculate the magnitude of force

experienced by the electron.  o Tm A e C

7 19 4 10 / , 1.6 10        .

c) A square coil of 10cm side and with 100turns is rotated at a uniform

speed of 500 revolutions per minute (rpm) about an axis at right angles

to a uniform field of 0.5T. Calculate the maximum emf produced in the

coil.

10. Answer any two numerical questions. 2x4=8

a) A beam of proton is accelerated through a potential difference of 2KV

and then enters a uniform magnetic field which is perpendicular to the

direction of proton beam. If the flux density is 0.5T, calculate the radius

of the path of the beam described. ( mass of proton = 1.710-27kg,

electronic charge = 1.610-19C)

b) Find the frequency of light which ejects electrons from a metal surface

are fully stopped by a retarding potential of 3V. The photoelectric effect

begins in this metal at frequency of 61014Hz.

(Planck's constant = 6.610-34Js)

c) Assuming that about 200 MeV energy is released per fission of 92U235

nuclei, what would be the mass of U235 consumed per day in the fission

reactor of power 1MW ?

11. A tuning fork of frequency 512Hz produces sound waves of wavelength

65cm in air at NTP. Calculate the increase in wavelength when the

temperature of air is 27oC. 4

12. A diffraction grating has 500 lines per mm and is illuminated normally with

monochromatic light of wavelength 589nm. Calculate the angle to the normal

at which second order diffraction maximum is observed and the number of

diffraction maxima obtained.