Competitive Exams: Physics MCQs (Practice-Test 21 of 35)

  1. A single slit is used to observe diffraction pattern with red light. On replacing the red light with violet light the diffraction pattern would be

    1. remain unchanged

    2. become narrower

    3. become broader

    4. disappear

  2. The thickness of a quarter-wave plate made of quartz for wavelength l = 5000 A, refractive indices mE = 1.553 and m0 = 1.543 is

    1. 5.00 × 10 − 3 cm

    2. 3.75 × 10 − 3 cm

    3. 2.50 × 10 − 3 cm

    4. 1.25 × 10 − 3 cm

  3. When unpolarised light gets reflected from a plane glass surface, it becomes partly polarized because glass

    1. is optically active

    2. rotates the components in the plane of incidence and those perpendicular to the plane of incidence by different amounts

    3. reflects the components of light parallel to the plane of incidence and those perpendicular to it by different amounts

    4. is a stereoisomer

  4. If a quarter wave-plate with its fast axis vertical is inserted into abeam of linearly polarized light oscillating at 450, then the emerging light will be

    1. linearly polarized

    2. vertically polarized

    3. left circularly polarized

    4. left elliptically polarized

  5. In a Fabry-Perot interferometer the circular fringes formed are referred to as fringes of

    1. equal thickness

    2. equal inclination

    3. equal chromatic order

    4. None of the above

  6. Scattering intensity of pure carbon tetrachloride is 6 units for 500. The scattering intensity for 4000 is

    1. 4.5 units

    2. 6.0 units

    3. 7.5 units

    4. 14.6 units

  7. A substance shows a Raman frequency shift of 4000 cm-1. If this mode is active in the infra-red, then the corresponding infrared adsorption band will be at

    1. 0.5 m

    2. 1.0 m

    3. 1.5 m

    4. 2.5 m

  8. The population inversion necessary for laser action used in solid state lasers is

    1. electrical discharge

    2. inelastic atom-atom collision

    3. direct conversion

    4. optical pumping

  9. A given amount of heat cannot be completely converted into work. How ever it is possible to convert a given amount of work completely into heat. This apparently contradictory statement results from the

    1. zero th law of thermodynamics

    2. first law of thermodynamics

    3. second law of thermodynamics

    4. third law of thermodynamics

  10. The work done, W, during as isothermal process in which the gas expands from an initial volume V1 to a final volume V2 is given by (R: Gas constant, T: Temperature)

    1. R (V2 − V1) loge (T1/T2)

    2. R (T2 − T1) loge (V1/V2)

    3. R T loge (V2/V1)

    4. 2 R T loge (V1/V2)

  11. The combined form of first and second law of thermodynamics is given by (P: Pressure V: Volume, T: Temperature, U: Internal energy, S: Entropy, Q: Quantity of heat)

    1. TdS = dU + PdV

    2. dQ = TdS + PdV

    3. dU = TdS + dQ

    4. TdS = dU-PdV

  12. The temperature of water (mass, m) increases from T1 to T2. If C is the specific heat capacity of water, then the total increase in entropy of water is given by

    1. mC (T2 − T1)

    2. MC loge T1/T2

    3. mC (T1 − T2)

    4. mC loge T2/T1

  13. Which one of the following Maxwell's relations leads to Clausius-Clapeyron equation?

    1. (T/V) S = - (p/S) V

    2. (T/P) S = (V/S) P

    3. (V/T) P = - (S/P) T

    4. (S/V) T = (P/T) V

  14. A perfect gas at 27 degree C is heated at constant pressure so as to doubles its volume. The temperature of the gas will now be

    1. 600 degree C

    2. 327 degree C

    3. 300 degree C

    4. 54 degree C

  15. Consider the following processes that take place in a Carnet cycle:

    1. Adiabatic expansion

    2. Adiabatic compression

    3. Isothermal expansion

    4. Isothermal compression

    The correct sequence of the above process is

    1. 1, 3, 4, 2

    2. 3, 1, 2, 4

    3. 3, 1, 4, 2

    4. 1, 3, 2, 4