# Class 12 Physics Chapter 10 Wave Optics MCQ Questions with answers

Wave Optics Class 12 MCQ Pdf is one of the best strategies to prepare for the CBSE Class 12 Board exam. If you want to complete a grasp concept or work on one’s score, there is no method except constant practice. Students can improve their speed and accuracy by doing more MCQ on Wave Optics Class 12, which will help them all through their board test.

## Wave Optics Class 12 MCQ Questions Free PDF

Class 12 Physics MCQ with answers are given here to chapter the Wave Optics. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Physics syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Wave Optics Class 12 MCQ Questions with answers pdf free download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving CBSE Class 12 Wave Optics MCQ with answers given below.

Question 1. The frequency of a light wave in a material is 2 × 1014 Hz and wavelength is 5000 Å. The refractive index of material will be
(a) 1.50
(b) 3.00
(c) 1.33
(d) 1.40

B

Question 2. Which one of the following phenomena is not explained by Huygen’s construction of wavefront ?
(a) Refraction
(b) Reflection
(c) Diffraction
(d) Origin of spectra

D

Question 3. The refractive index of water is 1.33. What will be the speed of light in water?
(a) 4 × 108 m/s
(b) 1.33 × 108 m/s
(c) 3 × 108 m/s
(d) 2.25 × 108 m/s

D

Question 4. A star, which is emitting radiation at a wavelength of 5000 Å, is approaching the earth with a velocity of 1.5 × 104 m/s. The change in wavelength of the radiation as received on the earth is
(a) 25 Å
(b) 100 Å
(c) zero
(d) 2.5 Å

A

Question 5. Light travels through a glass plate of thickness t and having a refractive index m. If c is the velocity of light in vacuum, the time taken by light to travel this thickness of glass is
(a) t/μc
(b) μt/c
(c) tmc
(d) tc/μ

B

Question 6. Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is 3/2 is
(a) 2 × 10–4 s
(b) 2 × 108 s
(c) 2 × 10–11 s
(d) 2 × 1011

C

Question 7. Green light of wavelength 5460 Å is incident on an air-glass interface. If the refractive index of glass is 1.5, the wavelength of light in glass would be (c = 3 × 108 m s–1)
(a) 3640 Å
(b) 5460 Å
(c) 4861 Å
(d) none of these.

A

Question 8. A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5. The wavelength of refracted light will be
(a) depend on intensity of refracted light
(b) same
(c) smaller
(d) larger.

C

Question 9. Ratio of intensities of two waves are given by 4 : 1. Then ratio of the amplitudes of the two waves is
(a) 2 : 1
(b) 1 : 2
(c) 4 : 1
(d) 1 : 4

A

Question 10. Interference is possible in
(a) light waves only
(b) sound waves only
(c) both light and sound waves
(d) neither light nor sound waves

C

Question 11. In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2°. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? (mwater = 4/3)
(a) 0.1°
(b) 0.266°
(c) 0.15°
(d) 0.05°

C

Question 12. In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes
(a) double
(b) half
(c) four times
(d) one-fourth

C

Question 13. In a Young’ double slit experiment if there is no initial phase difference between the light from the two slits, a point on the screen corresponding to the fifth minimum has path difference.
(a) 5.λ/2
(b) 10.λ/2
(c) 9.λ/2
(d) 11.λ/2

C

Question 14. Young’s double slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in air. The refractive index of the medium is nearly
(a) 1.59
(b) 1.69
(c) 1.78
(d) 1.25

C

Question 15. In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength l of the light used is 5896 Å and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0.20°. To increase the fringe angular width to 0.21° (with same l and D) the separation between the slits needs to be changed to
(a) 1.8 mm
(b) 1.9 mm
(c) 2.1 mm
(d) 1.7 mm

B

Question 16. The intensity at the maximum in a Young’s double slit experiment is I0. Distance between two slits is d = 5l, where l is the wavelength of light used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance D = 10d ?
(a) 3/4 I0
(b) I0/2
(c) I0
(d) I04

B

Question 17. In the Young’s double slit experiment, the intensity of light at a point on the screen where the path difference l is K, (l being the wavelength of light used). The intensity at a point where the path difference is l/4 will be
(a) K
(b) K/4
(c) K/2
(d) zero

C

Question 18. Two slits in Young’s experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern, Imax /I min is
(a) 49/121
(b) 4/9
(c) 9/4
(d) 121/49

C

Question 19. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths l1 = 12000 Å and l2 = 10000 Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?
(a) 4 mm
(b) 3 mm
(c) 8 mm
(d) 6 mm

D

Question 20. Colours appear on a thin soap film and on soap bubbles due to the phenomenon of
(a) interference
(b) dispersion
(c) refraction
(d) diffraction.

A

Question 21. In Young’s double slit experiment the distance between the slits and the screen is doubled. The separation between the slits is reduced to half. As a result the fringe width
(a) is halved
(b) becomes four times
(c) remains unchanged
(d) is doubled.

B

Question 22. In a Fresnel biprism experiment, the two positions of lens give separation between the slits as 16 cm and 9 cm respectively. What is the actual distance of separation?
(a) 13 cm
(b) 14 cm
(c) 12.5 cm
(d) 12 cm

D

Question 23. If yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by monochromatic blue light of the same intensity
(a) fringe width will decrease
(b) fringe width will increase
(c) fringe width will remain unchanged
(d) fringes will becomes less intense

A

Question 24. Interference was observed in interference chamber where air was present, now the chamber is evacuated, and if the same light is used, a careful observer will see
(a) no interference
(b) interference with brighter bands
(c) interference with dark bands
(d) interference with larger width.

D

Question 25. In Young’s experiment, two coherent sources are placed 0.90 mm apart and fringes are observed one metre away. If it produces second dark fringe at a distance of 1 mm from central fringe, the wavelength of monochromatic light is used would be
(a) 60 × 10–4 cm
(b) 10 × 10–4 cm
(c) 10 × 10–5 cm
(d) 6 × 10–5 cm

D

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Question 26. In Young’s double slit experiment carried out with light of wavelength (l) = 5000 Å, the distance between the slits is 0.2 mm and the screen is at 200 cm from the slits. The central maximum is at x = 0. The third maximum (taking the central maximum as zeroth maximum) will be at x equal to
(a) 1.67 cm
(b) 1.5 cm
(c) 0.5 cm
(d) 5.0 cm

B

Question 27. Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is

A

Question 28. In Young’s double slit experiment, the fringes width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 , without disturbing the geometrical arrangement, the new fringe width will be
(a) 0.30 mm
(b) 0.40 mm
(c) 0.53 mm
(d) 450 micron.

A

Question 29. An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of
(a) small focal length and large diameter
(b) large focal length and small diameter
(c) large focal length and large diameter
(d) small focal length and small diameter.

C

Question 30. A linear aperture whose width is 0.02 cm is placed immediately in front of a lens of focal length 60 cm.
The aperture is illuminated normally by a parallel beam of wavelength 5 × 10–5 cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is
(a) 0.10 cm
(b) 0.25 cm
(c) 0.20 cm
(d) 0.15 cm

D

Question 31. The ratio of resolving powers of an optical microscope for two wavelengths l1 = 4000 Å and l2 = 6000 Å is
(a) 9 : 4
(b) 3 : 2
(c) 16 : 81
(d) 8 : 27

B

Question 32. In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used.
What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?
(a) 0.5 mm
(b) 0.02 mm
(c) 0.2 mm
(d) 0.1 mm

C

Question 33. A beam of light of l = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is
(a) 1.2 cm
(b) 1.2 mm
(c) 2.4 cm
(d) 2.4 mm

D

Question 34. At the first minimum adjacent to the central maximum of a single-slit diffraction pattern, the phase difference between the Huygen’s wavelet from the edge of the slit and the wavelet from the midpoint of the slit is

A

Question 35. A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct?
(a) The angular width of the central maximum will decrease.
(b) The angular width of the central maximum will be unaffected.
(c) Diffraction pattern is not observed on the screen in the case of electrons.
(d) The angular width of the central maximum of the diffraction pattern will increase.

A

Question 36. A parallel beam of light of wavelength l is incident normally on a narrow slit. A diffraction pattern formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of slit is
(a) 2Π
(b) 3Π
(c) 4Π
(d) Πl

C

Question 37. A telescope has an objective lens of 10 cm diameter and is situated at a distance of one kilometre from two objects. The minimum distance between these two objects, which can be resolved by the telescope, when the mean wavelength of light is 5000 Å, is of the order of
(a) 0.5 m
(b) 5 m
(c) 5 mm
(d) 5 cm

C

Question 38. The angular resolution of a 10 cm diameter telescope at a wavelength of 5000 Å is of the order of

C

Question 39. Ray optics is valid, when characteristic dimensions are
(a) much smaller than the wavelength of light
(b) of the same order as the wavelength of light
(c) of the order of one millimetre
(d) much larger than the wavelength of light.

D

Question 40. Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them, which are situated at a distance of 50 meter from eye? (The wavelength of light is 5000 Å.)
(a) 2.32 m
(b) 4.28 mm
(c) 1.25 cm
(d) 12.48 cm

C

Question 41. The Brewsters angle ib for an interface should be
(a) 0° < ib < 30°
(b) 30° < ib < 45°
(c) 45° < ib < 90°
(d) ib = 90

C

Question 42. In Fresnel’s biprism expt., a mica sheet of refractive index 1.5 and thickness 6 × 10–6 m is placed in the path of one of interfering beams as a result of which the central fringe gets shifted through 5 fringe widths. The wavelength of light used is
(a) 6000 Å
(b) 8000 Å
(c) 4000 Å
(d) 2000 Å

A

Question 43. A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focussed by a convex lens on a screen placed in focal plane.
The first minimum will be formed for the angle of diffraction equal to
(a) 0°
(b) 15°
(c) 30°
(d) 50°

C

Question. 44 A radar sends radiowaves of frequency v towards an aeroplane moving with velocity va. A change Dn is observed in the frequency of reflected waves which is higher than original frequency. The velocity of aeroplane is (va << c)
(a) cΔv/v
(b) 2cΔv/Δv
(c) cΔv/2v
(d) Δv/2cv

C

Question 45. If a wave can be polarized, it must be
(a) a transverse wave
(b) a longitudinal wave
(c) a sound wave
(d) a stationary wave

A

Question 46. In Young’s double slit experiment, we get 10 fringes in the field of view of monochromatic light of wavelength 4000Å. If we use monochromatic light of wavelength 5000Å, then the number of fringes obtained in the same field of view is
(a) 8
(b) 10
(c) 40
(d) 50

A

Question 47. The phenomenon by which stars recedes from each other is explained by
(a) black hole theory
(b) neutron star theory
(c) white dwarf
(d) red shift

D

Question 48. The phenomenon of interference is shown by
(a) longitudinal mechanical waves only
(b) transverse mechanical waves only
(c) non-mechanical transverse waves only
(d) All of the above

D

Question 49. In Young’s double slit experiment, if the slit widths are in the ratio 1 : 2, the ratio of the intensities at minima and maxima will be
(a) 1 : 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 9

D

Question 50. The transverse nature of light is shown by
(a) interference of light
(b) refraction of light
(c) polarization of light
(d) dispersion of light

C

Question 51. Angular width (B) of central maxima of a diffraction pattern of a single slit does not depend upon
(a) distance between slit and source
(b) wavelength of the light used
(c) width of slit
(d) frequency of light used