CHAPTER 9 PHYSICAL OPTICS

 

9.1      Multiple choice questions

1.      Who presented the corpuscle theory of light?
(a) Huygen	(b) Newton
(c) Young	(d) Maxwell
2.      Which phenomenon does not explain the of wave theory of light?
(a) Polarization	(b) Interference
(c) Diffraction	(d) Compton effect
3.      Interference of lights occur when their source is;
(a) Monochromatic	(b) Coherent
(c) Closed to each other	(d) All of these
4.      In young’s double slit experiment, when the distance between two slits is halved and distance between slits and screen is doubled then the fringe width is:
(a) Remain same	(b) Halved
(c) Doubled	(d) Quadrupled
5.      In young double slit experiment, the ratio of fringe width of bright to dark fringe is
(a) 1:1	(b) 1:2
(c) 2:1	(d) 2:3
6.      In the Young’s double slit experiment if white light is used
(a) Bright fringes will be seen	(b) Dark fringes will be seen
(c) Alternate dark and bright fringes will be seen	(d) No interference fringes will be seen
7.      When light is reflected from dense medium to rare medium then its path
(a) Remains same	(b) Changes by λ/2
(c) changes by λ	(d) Changes by 3λ/2
8.      Michelson interferometer is an optical instrument which is being used for the measurement of;
(a) Velocity	(b) Frequency
(c) Amplitude	(d) Wavelength
9.      Mathematical condition of destructive interference in thin film is;
(a) mλ	(b)mλ/2
(c) (m+1/2)λ	(d) (m+λ)
10.  Which parameter of light does not change when light is reflected from dense
(a) Frequency	(b) Wavelength
(c) Velocity	(d) Amplitude
11.  In Michelson interferometer, a fringe is changed by changing the position of movable mirror at a distance
(a) λ/4	(b) λ/2
(c) λ	(d) 2λ
12.  Number of slits in a diffraction grating depends upon.
(a) Speed of light	(b) Frequency of light
(c) Wavelength of light	(d) Amplitude of light
13.  If the wavelength of the incident x-rays is 2 x 10-10 m then the required number of slits per centimeter for its diffraction should be
(a) 5 x 106	(b) 5 x 107
(c) 5 x 108	(d) 5 x 1010
14.  Which phenomenon has confirmed that light is transverse wave.
(a) Interference	(b) Diffraction
(c) Reflection	(d) Polarization
15.  If the unpolarized incident light with intensity ‘I’ is polarized to polaroid sheet, then the intensity of plane polarized light will be;
(a) I/2	(b) √I
(c) I	(d)2I
16.  Which one of the following cannot be polarized.
(a) X-rays	(b) Radio waves
(c) Ultraviolet waves	(d) Sound waves

 

Answers

1. (b) Newton
2. (d) Compton effect
3. (d) All of these
4. (a) Remain same
5. (a) 1:1
6. (d) No interference fringes will be seen
7. (b) Changes by 
8. (d) Wavelength
9. (a)  mλ
10. (a) Frequency
11. (b) λ/2
12. (c) Wavelength of light
13. (b) 5 x 10⁷
14. (d) Polarization
15. (a) I/2
16. (d) Sound waves

9.2      Short question

14. Can visible light produce interference fringes?

ans.    Yes, visible light can produce interference fringes if source of visible light is coherent and monochromatic.

15. In Young’s double slit experiment, one of the slits is covered with blue filter and the other with red filter. What would be the pattern of light intensity on the screen?

ans.    Pattern would not be form on the screen because red light and blue light have different frequencies (not coherent source ).

16. State whether the fringe width for bright and dark fringes in Young's interference always constant?

17. Find the grating element of the diffraction grating containing 2000 lines/cm?

9.3      Numerical problems

1. Light of wavelength 400nm is allowed to illuminate the slits of Young’s experiment. The separation between the slits is 0.10m m and the distance of the screen from the slits where interference effects are observed is 20 cm. At what angle the first minimum will fall? What will be the linear distance on the screen between adjacent maxima?

3. Interference fringes were produced by two slits spaced 0.2mm apart, on a screen at a distance of 150 cm from the slits, the third bright fringe is found to be displaced 7.5mm from the central fringes. What is the wavelength of light producing the fringes?

4. Green light of wavelength 540nm is diffracted by grating having 2000 lines/cm. (a) Compute the angular deviation of the third order image. (b) Is 12^th order image possible?

8. Calculate the distance through which the mirror of the Michelson Interferometer has to be displaced between two consecutive positions of maximum distinctness of D₁ and D₂ lines of sodium. The wavelength of D₁ line is 5890Å and of D₂ line is 5896 Å.

CHAPTER 7 OSCILLATIONS

 

7.1      Multiple choice questions.

1.      The acceleration of a body in simple harmonic motion is
(a) Zero at each point	(b) Remain same at each point
(c) Maximum at mean position	(d) Maximum at extreme position
2.      What is the value of a spring constant when a 100 g mass is connected with a spring and it is accelerated 0.5 ms-2 through a displacement of 5cm?
(a) 0.1 N m-1	(b) 0.5 N m-1
(c) 1 N m-1	(d) 5 N m-1
3.      If a spring of forced constant K is cut into two equal parts. Then the spring constant of each half is
(a) k/2	(b) 2k
(c) k	(d) k/ √2
4.      When a body is performing S.H.M then at its extreme position.
(a) Displacement is zero	(b) Amplitude is zero
(c) Velocity is a zero	(d) P.E is zero
5.      A particle is executing S.H.M along a straight line with amplitude A. Its kinetic energy is maximum when its displacement is
(a) ±A	(b) ±A/2
(c) Zero	(d) ±A/√2
6.      The time period of a body attached to a spring depends upon
(a) Amplitude	(b) Mass
(c) Length	(d) Displacement
7.      When the length of the pendulum is increased four times then its time period is increased
(a) One time	(b) Two time
(c) Three time	(d) Four time
8.      What is the frequency of the body when its time period is 2 seconds?
(a) 1 Hz	(b) 2 Hz
(c) 0.2 Hz	(d) 0.5 Hz
9.      A second’s pendulum is one who has a time period of
(a) 1 s	(b) 2 s
(c) 1/2 s	(d) 0.2 s
10.  In S.H.M at what distance from mean position in terms amplitude x0, where K.E and P.E have equal value?
(a) 0.51x0	(b) 0.61x0
(c) 0.71x0	(d) 0.81x0
11.  The instantaneous K.E of a mass attached to the end of an elastic spring is
(a) k(x20 - x2)	(b) k(x20 + x2)
(c) k(x2 - x20 )	(d) k(x - x0 )
12.  In S.H.M., we have the conservation of
(a) Kinetic energy	(b) Potential energy
(c) Total energy	(d) Mechanical energy
13.  A free oscillation has constant
(a) Energy	(b) Amplitude
(c) Frequency	(d) All of these
14.  When damping force is equal to the force oscillation then the damping is called.
(a) Under damping	(b) Critical damping
(c) Over damping	(d) No damping
15.  A resonance is occurred when driving frequency is
(a) Less than the natural frequency	(b) Greater than natural frequency
(c) Equal to the natural frequency	(d) Equal to zero
16.  In the absence of damping force, when driving frequency is equal to Oscillating frequency then the amplitude of the oscillation will become
(a) Zero	(b) Minimum
(c) Maximum	(d) Infinity
17.  Food is cooked in a microwave oven by the effect of
(a) Interference	(b) Mechanical resonance
(c) Magnetic resonance	(d) Electric resonance

 

Answers

1. (c) Maximum at mean position
2. (c) 1 N m^-1
3. (b) 2k
4. (c) Velocity is a zero
5. (c) Zero
6. (b) Mass
7. (b) Two time
8. (d) 0.5 Hz
9. (b) 2 s
10. (c) 0.71x₀
11. (a) k(x²₀ - x²)
12. (d) Mechanical energy
13. (c) Frequency
14. (b) Critical damping
15. (c) Equal to the natural frequency
16. (c) Maximum
17. (c) Magnetic resonance

7.2      Short questions

7. Show that in S.H.M the acceleration is zero when the velocity is maximum, and the velocity is zero when the acceleration is maximum.

15. What happens to the period of a simple pendulum if its length is doubled?

7.3      Numerical problems

1. When a 600 g of mass is suspended at the end of a vertical spring and the spring f stretches 0.45 m. What is the spring constant of the spring and how much further will Stretch? If an additional mass of 600 g is hung from it.

2. A 2 kg mass is executing S.H.M and makes 4 vibrations per second. Calculates the acceleration and the restoring force acting in the body when its displacement from mean position is 7 cm.

6. How much time period of a simple pendulum is increased by increasing it length from 0.8 m to 0.993 m?

8. A car of mass 1300 kg is constructed using a frame supported by four spring each spring has a spring constant 20000 Nm^-1. If two people riding in the car have a combined mass of 160 kg, find the frequency of vibration of the Car. When it is driven over a pot-hole in the road. Assume the weight is evenly disturbed.