Time Allowed: 3 hours
Maximum Marks: 100


Note: Attempt FIVE questions in all, including Question No. 8, which is compulsory. All questions carry equal marks.


Q1. Three vectors are given by:
a = 3i + 3j -2k
b = -i - 4j + 2k
c = 2i + 2j – k
Find (i) a. (b. × c), (ii) a. (b. + c), (iii) a. × (b + c)

Q2. (a) State the basic postulates of special theory of Relativity. Discuss the effect of relative uniform motion on Mass, Length and Time.
(b) A rod lies parallel to the x-axis of reference frame S, moving along this axis at a speed of 0.632 C. Its rest length is 1.68m. What will be its measured length in frame S?

Q3. (a) What is meant by Interference of Light? Also distinguish between Constructive Interference and Destructive Interference.
(b) Derive an expression for the Resolving Power of a plane diffraction grating.
(c) Monochromatic light emitted from He-Ne laser source with λ = 632.8 nm is incident normally on a diffraction grating containing 6000 lines per cm. Find the angles at which one would observe the first order maximum and the second order maximum. Will it be possible to observe the third order maximum as well?

Q4. (a) Differentiate between Travelling Waves and Standing Waves.
(b) Prove that the Rate of Transfer of Energy in wave motion depends on the square of the wave amplitude and square of the wave frequency. (marks 10)
(c) Spherical waves travel from a source of waves whose power output, assumed constant, is P. What will be the wave intensity I at a distance from the source?

Q5. Write an essay on the production and measurement of low temperatures.

Q6. State and explain the First Law of Thermodynamics. Discuss its applications in the case of
a. Adiabatic
b. Isothermal
c. Isochoric
d. Isobaric Processes

Q7. Write notes on any TWO of the following:
a. Bernoulli’s Theorem
b. Laser and its Applications
c. Brownian Motion

Q8. Write only the correct answer in the Answer Book. Don’t reproduce the questions.

1. The vector in space has:
a. Three components
b Two components
c. One component
d. None of these


2. The correct relation is:
a. a . b = b . a
b a . b ≠ b . a
c. a × b = b × a
d. a . b = b × a

3. N.s./m^2 is the SI unit of:
a. Surface tension
b. Viscosity
c. Force
d. Momentum
e. None of these

4. Antinodes are points where:
a. Strain is maximum
b. Frequency is maximum
c. Wave length is maximum
d. Amplitude is maximum
e. None of these

5. When the mass and speed of a body are doubled, the momentum becomes:
a. 16 times
b. 8 times
c. 4 times
d. 3 times
e. None of these

6. Efficiency of carnot engine is 100% when temperature of sink is:
a. Zero
b. Infinite
c. Equal to source
d. None of these

7. For gases obeying Boyle’s Law, if pressure is doubled, volume becomes:
a. Double
b. One half
c. Three times
d. No change

8. Distance between an antinodes and an adjacent node is:
a. λ
b. 2
c. λ/2
d. λ/4

9. Total energy of a particle performing S.H.M. is directly proportional to:
a. The amplitude
b. The square root of amplitude
c. The square of amplitude
d. The reciprocal of amplitude
e. None of these

10. Frequencies less than 20 Hz are called:
a. Supersonics
b. Ultrasonics
c. Infrasonics
d. None of these

11. Laser is an intense beam of light which is
a. Monochromatic
b. Coherent
c. Collimated
d. All of the above

12. The change in entropy ∆S of a system is given by:
a. ∆S = ∆Q/T
b. ∆S = T ∆ Q
c. ∆S = T/∆Q
d. None of these

13. The particle nature of light if evidenced from:
a. Polarisation
b. Interference
c. Diffraction
d. Photoelectric Effect
e. None of these

14. Sound waves are
a. Electromagnetic waves
b. Mechanical waves
c. Transverse waves
d. Radio waves
e. None of these

15. Kilo Watt Hour (KWh) is a unit of:
a. Electric Flux
b. Electric Field
c. Electric Energy
d. Electric Potential
e. None of these

16. All motions are:
a. Absolute
b. Uniform
c. Relative
d. None of these

17. The normal human body temperature on Fahrenheit scale is:
a. 96°F
b. 98.6°F
c. 99°F
d. 100°F

18. We get light inside a room in daytime due to:
a. Diffraction
b. Interference
c. Polarisation
d. Refraction
e. None of these

19. The radiation which gives sense of heat is called:
a. Visible light
b. Invisible light
c. Infra-red radiation
d. Ultra violet rays
e. None of these

20. Heat death will occur when:
a. Temperature is maximum
b. Temperature is minimum
c. Heat energy is zero
d. All bodies are at the same temperature
e. None of these

Time Allowed: 3 hours
Maximum Marks: 100


Note: Attempt FIVE questions in all, including Question No. 8, which is compulsory. All questions carry equal marks.

Q1. (a) What is a point charge? Why do we take a point charge while estimating the electric field intensity of a system of charge?
(b) What do you understand from Coulomb’s law and Gauss’s law? Do they represent the same fact (law)? If yes – how; if no – why?
(c) a 24-volt lamp has a resistance of 8 ohms. What resistance must be placed in series with it, if it is to be used in a 117-volt line?

Q2. (a) What requirements must be met to form an electric circuit? Is there any similarity between an electric and a magnetic circuit? Explain the terms MMF and reluctance.
(b) Discuss the statement: “In case of a transformer whatever is gained is voltage is lost in current.”
(c) What causes the magnetism? Differentiate between Dia-, Para-, Ferromagnetic materials.

Q3. (a) In how many ways electrons can be emitted from various materials? Describe thermionic emission in detail and establish the Child’s law.
(b) What is meant by modulation? Describe its various types and show that a 100% amplitude modulation increases the radiated power by 50%.
(c) Calculate the frequency of radio waves coming out of an oscillating circuit containing a capacitor of 0.02 microfarad and an inductor of 8 microhenry.

Q4. (a) How would you calculate and of a triode from its characteristic curves?
(b) What is rectification? How is it achieved? Draw fully labelled circuits for half-wave and full-wave rectifiers.
(c) Explain how P-, and N-type semiconductors are produced? Elaborate the concept of a “hole”.

Q5. (a) Discuss various models put forward to explain the atomic structure/ describe the advantages and disadvantages of each model and show how the shortcomings of one model were overcome by the subsequent model?
(b) Explain the significance of Pauli’s principle.
(c) An electron is moving with a velocity of m/s. Calculate the energy in electron-volts. Mass of electron is given as g?

Q6. (a) Obtain expression for the wave numbers of lines belonging to different series of hydrogen atom. Draw suitable diagrams to show hydrogen spectrum.
(b) Find de-Broglie wave length of helium atoms (mass kg) having average velocity m/s. Planck’s constant is Js.

Q7. (a) Explain that radioactive rays are of inter-nuclear origin.
(b) What is chain reaction in nuclear fission? Explain controlled and uncontrolled chain reactions.

Q8.Write only the correct answer in the Answer Book. Don’t reproduce the questions.

(1) A negative electric charge:
(a)Interacts only with positive charges
(b)Interacts only with negative charges
(c)Interacts with both positive and negative charges
(d)May interact with either positive or negative charges, depending on circumstances
(e)None of these

(2) Ten thousand electrons are removed from a neutral pith ball. Its charge is now
(a) +1.6×〖10〗^(-15)
(b) +1.6×〖10〗^(-23)
(c) -1.6 ×〖10〗^(-15) C
(d) -1.6×〖10〗^(-23) C
(e)None of these

(3) If air is replaced by an other medium, the force between two charges:
(a)Increases
(b)Decreases
(c)Remains the same
(d)May increase or decrease depending upon the nature of medium
(e)None of these

(4) The result of placing soft iron inside a coil is:
(a)Increase in magnetic flux
(b)Decrease in magnetic flux
(c)No change in the magnetic flux
(d)None of these

(5) The appearance of an electric field in a conductor when it is moved across a magnetic field is an example of:
(a)Lenz’s law
(b)Ohm’s law
(c)Electromagnetic induction
(d)Magnetic flux
(e)None of these

(6) The primary winding of a transformer has 200 turns and its secondary winding has 50 turns, if the current in the secondary winding is 40 A, the current in the primary is:
(a)10 A
(b)80 A
(c)160 A
(d)8000 A
(e)None of these

(7) The energy content of a charged capacitor resides in its:
(a)Plates
(b)Potential difference
(c)Charge
(d)Electric field
(e)None of these

(8) In an ac-circuit, the voltage:
(a)Leads the current
(b)Lags the current
(c)Is the phase with the current
(d)Any of the above, depending on the circumstances
(e)None of these

(9) Amount of energy liberated in Fission reaction of one atom of is nearly:
(a)200 MeV
(b)20 MeV
(c)20 eV
(d)200 eV
(e)None of these

(10) Substance which can be used as moderator in a reactor is:
(a)Graphite
(b)Heavy water
(c)Cadmium
(d)Uranium
(e)None of these

(11) The half-life of phosphorus 32 is 15 days. A given mass of phosphorous 32 will reduce to of its original mass in:
(a)60 days
(b)30 days
(c)45 days
(d)90 days
(e)None of these

(12) Which of the following fundamental particles is heaviest:
(a)Electron
(b)Muon
(c)Neutrino
(d)Meson
(e)None of these

(13) Fission reaction U^235 of is:
(a)Exothermic
(b)Endothermic
(c)None of these

(14) For an atom having atomic number, Z, and atomic weight, A, the number of neutrons in a nucleus is:
(a)A
(b)Z
(c)A+Z
(d)A-Z

(15) Normally the emitter of the transistor has to be:
(a)Forward biased
(b)Reverse biased
(c)May be forward biased or reverse biased
(d)May not be biased
(e)None of these

(16) The inductance in a coil plays the same role as:
(a)Inertia plays in mechanics
(b)Energy plays in mechanics
(c)Momentum plays in mechanics
(d)None of these

(17) If the current flowing through a lamp drops by 1 per cent, what will be the percentage decrease 1 power?
(a)0.01%
(b)1%
(c)2%
(d)4%
(e)None of these

(18) Modern physical theories indicate that:
(a)All particles exhibit wave behaviour
(b)Only moving particles exhibit wave behaviour
(c)Only charged particles exhibit wave behaviour
(d)Only uncharged particles exhibit wave behaviour
(e)None of these

(19) A neon sign does not produce:
(a)A line spectrum
(b)An emission spectrum
(c)An absorption spectrum
(d)Photons
(e)None of these

(20) The splitting of the spectral limes of an element when it radiates in a magnetic field is known as:
(a)The Schrodinger effect
(b)The Zeeman effect
(c)Induced emission
(d)Population inversion

__________________
Regards,
P.R.