# Wave Optics Questions

### Wave Optics Question Bank:

Ques. Polarised glass is used in sun glasses because
(a) It reduces the light intensity to half an account of polarisation
(b) It is fashionable
(c) It has good colour
(d) It is cheaper

Ans. (a)

Ques. Young’s experiment establishes that
(a) Light consists of waves
(b) Light consists of particles
(c) Light consists of neither particles nor waves
(d) Light consists of both particles and waves

Ans. (a)

Ques. A single slit of width a is illuminated by violet light of wavelength 400 nm and the width of the diffraction pattern is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 600 nm, the width of the diffraction pattern is
(a) The pattern vanishes and the width is zero
(b) y / 3
(c) 3y
(d) None of these

Ans. (c)

Ques. In Young’s double slit experiment, if the slit widths are in the ratio 1 : 9, then the ratio of the intensity at minima to that at maxima will be
(a) 1
(b) 1/9
(c) 1/4
(d) 1/3

Ans. (c)

Ques. When a compact disc is illuminated by a source of white light. Coloured ‘lanes’ are observed. This is due to
(a) Dispersion
(b) Diffraction
(c) Interference
(d) Refraction

Ans. (b)

Ques. In a Young’s double slit experiment, the central point on the screen is
(a) Bright
(b) Dark
(c) First bright and then dark
(d) First dark and then bright

Ans. (a)

Ques. In Young’s double slit interference experiment, the slit separation is made 3 fold. The fringe width becomes
(a) 1/3 times
(b) 1/9 times
(c) 3 times
(d) 9 times

Ans. (a)

Ques. When a thin metal plate is placed in the path of one of the interfering beams of light
(a) Fringe width increases
(b) Fringes disappear
(c) Fringes become brighter
(d) Fringes becomes blurred

Ans. (b)

Ques. Biological importance of Ozone layer is
(a) It stops ultraviolet rays
(b) Ozone rays reduce green house effect
(c) Ozone layer reflects radio waves
(d) Ozone layer controls Oxygen and Hydrogen radio in atmosphere

Ans. (a)

Ques. In Youngâ€™s double slit experiment, the central bright fringe can be identified
(a) By using white light instead of monochromatic light
(b) As it is narrower than other bright fringes
(c) As it is wider than other bright fringes
(d) As it has a greater intensity than the other bright fringes

Ans. (a)

Ques. The sun is rotating about its own axis. The spectral lines emitted from the two ends of its equator, for an observer on the earth, will show
(a) Shift towards red end
(b) Shift towards violet end
(c) Shift towards red end by one line and towards violet end by other
(d) No shift

Ans. (c)

Ques. Which of the following is not a property of light?
(a) It requires a material medium for propagation
(b) It can travel through vacuum
(c) It involves transportation of energy
(d) It has finite speed

Ans. (a)

Ques. If a source of light is moving away from a stationary observer, then the frequency of light wave appears to change because of
(a) Doppler’s effect
(b) Interference
(c) Diffraction
(d) None of these

Ans. (a)

Ques. Infrared radiation was discovered in 1800 by
(a) William Wollaston
(b) William Herschel
(c) Wilhelm Roentgen
(d) Thomas Young

Ans. (b)

Ques. A single slit of width 0.20 mm is illuminated with light of wavelength 500 nm. The observing screen is placed 80 cm from the slit. The width of the central bright fringe will be
(a) 1 mm
(b) 2 mm
(c) 4 mm
(d) 5 mm

Ans. (c)

Ques. The electromagnetic waves do not transport
(a) Energy
(b) Charge
(c) Momentum
(d) Information

Ans. (b)

Ques. Doppler’s effect in sound in addition to relative velocity between source and observer, also depends while source and observer or both are moving. Doppler effect in light depend only on the relative velocity of source and observer. The reason of this is
(a) Einstein mass – energy relation
(b) Einstein theory of relativity
(c) Photoelectric effect
(d) None of these

Ans. (b)

Ques. Ozone is found in
(a) Stratosphere
(b) Ionosphere
(c) Mesosphere
(d) Troposphere

Ans. (a)

Ques. In Fresnelâ€™s biprism experiment, on increasing the prism angle, fringe width will
(a) Increase
(b) Decrease
(c) Remain unchanged
(d) Depend on the position of object

Ans. (b)

Ques. In case of linearly polarized light, the magnitude of the electric field vector:
(a) Does not change with time
(b) Varies periodically with time
(c) Increases and decreases linearly with time
(d) Is parallel to the direction of propagation

Ans. (b)

Ques. In Young’s double slit experiment, if one of the slit is closed fully, then in the interference pattern
(a) A bright slit will be observed, no interference pattern will exist
(b) The bright fringes will become more bright
(c) The bright fringes will become fainter
(d) None of these

Ans. (a)

Ques. Assuming that universe is expanding, if the spectrum of light coming from a star which is going away from earth is tested, then in the wavelength of light
(a) There will be no change
(b) The spectrum will move to infrared region
(c) The spectrum will seems to shift to ultraviolet side
(d) None of these

Ans. (b)

Ques. The apparent wavelength of the light from a star moving away from the earth is 0.01% more than its real wavelength. Then the velocity of star is
(a) 60 km/sec
(b) 15 km/sec
(c) 150 km/sec
(d) 30 km/sec

Ans. (d)

Ques. If the shift of wavelength of light emitted by a star is towards violet, then this shows that star is
(a) Stationary
(b) Moving towards earth
(c) Moving away from earth
(d) Information is incomplete

Ans. (b)

Ques. What will be the angle of diffracting for the first minimum due to Fraunhoffer diffraction with sources of light of wave length 550 nm and slit of width 0.55 mm?

Ans. (a)