# Objective questions of wave optics

### Student’s as we know  from this  year , in CBSE 12th board examination ( physics )  there will be 20 , 1- mark questions . therefore we just posted some  objective questions of wave optics , so that students can practice well all kind of objective questions of wave optics   in short time .

Objective questions of wave optics

1. Newton has postulated his corpuscular theory on the basis of , (a) Newton’s ring (b) color due to thin film (c) dispersing of light (d) rectilinear propagation of light.
2. The wavefront is a surface in which ; (a) all points are on the same phase(b) there are pair of points in opposite phase (c) there are pairs of points with phase difference 900 (d)there are no relation between the phase.
3. The concepts of secondary wavelets from all points on a wave front was proposed by ; (a) Newton (b) Huygen (c) Faraday (d) Raman.
4. Huygen’s concepts of secondary waves ; (a) allow us to find the focal length of  thin lens  (b) gives the magnifying power of thin lens (c) is a geometrical method to find the wavelength (d)is used to find the velocity of light.
5. For constructive interference to take place between two monochromatic light waves of wavelength λ , the path difference should be ; (a) (2n-1)λ/4 (b) (2n-1)λ/2 (c) nλ (d)(2n+1)λ/2
6. Two light sources are coherent when ; (a) their amplitudes are equal (b) their frequency are equal (c) their wavelengths are equal (d)their frequencies are equal and their phase difference is constant.
7. Ratio of intensity of two waves is given by 4:1 , the ratio of amplitudes of their waves is ; (a) 2:1 (b)1:2 (c) 4:1 (d)1:4
8. If the ratio of intensities of two waves causing interference be 9:4 then the ratio of the resultant maximum and minimum intensity will be : ; (a) 9:4(b) 3:2 (c) 25:1 (d)5:1 .

1. In young’s double slit experiment , if monochromatic light used is replaced by white light , then ; (a) no fringes are observed (b) all bright fringes becomes white (c) all fringes have colour between violet and red  (d)only central fringes is white and all other fringes are coloured .
2. Two coherent monochromatic light beams of intensity I and 4I are superposed , the max and min. possible intensities in the resulting beam are  ; (a) 5I and I (b) 5I and 3I (c) 9I and I (d) 9I and 3I
3. If two waves , each of intensities I0 , having the same frequency but differing by constant phase angle of 600 , superpose at a certain point in space , then the intensity of resultant wave is ; (a) 2I0 (b) √3 I0 (c) 3I0 (d) 4I0
4. Two monochromatic waves each of intensity I , have constant phase difference of ɸ , if these waves superpose , then the intensity of resulting wave is  ; (a) 4I (b) 4Icosɸ (c) 4Icos2ɸ (d) 4I cos2 (ɸ/2)
5. Two monochromatic waves of same amplitude ‘a’ ,have random phase difference between them . when these wave superpose , then the amplitude of resulting wave is given by ; (a) √2a  (b) 2a (c) 4a (d)zero .
6.  The contrast in the fringes in any interference pattern depends on ; (a) fringe width (b)wavelength (c) intensity ratio of the sources (d) distance between the sources
7. In young’s double slit experiment if the distance between the slits is made 3-folds, the fringe width becomes ; (a) 1/3 folds (b) 3 folds (c) 1/9 folds (d) 9 folds .
8. In Young’s double slit experiments the separation between the is halved and separation between the slits and screen is doubled , the fringe width is ; ; (a) unchanged (b) halved (c) doubled (d) quadrupled .
9. Yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by blue light of the same intensity ; (a) fringe width will decrease (b) fringe width will increase (c) fringe width will remain unchanged (d) fringe will become less intense .
10. Two light waves are coherent if they are obtained from a single monochromatic source by ; ; (a) division of amplitude only (b) division of wavefront only (c) both of the above (d) none of the above.

1. In an interference experiment monochromatic light is replaced by white light , we will see , ; (a) uniform illumination on the screen (b) uniform darkness in the screen (c) equally spaced white and dark bands (d) a few coloured bands and then uniform illumination .
2. In Young’s double slit experiment the fringe width is found to be 0.4 mm . if the whole apparatus is immersed in water of refractive index 4/3 without disturbing the original geometric arrangement , then new fringe width will be ; (a) 0.3mm (b)0.40mm  (c) 0.53mm (d )450 microns .
3. Two waves are said to be coherent if they have ; (a) same wave length (b) same amplitude (c) same amplitude and save wavelength (d) same wavelength and constant phase difference .
4. In a young’s double slit experiment fringe width is equal to 1mm , then the distance of the nearest bright fringe from the central fringe will be ; (a) 1mm (b) 0.5mm (c) 2mm (d) insufficient data ,
5. In young’s double slit experiment . if width of the slit s is increased keeping other parameters constant , then the interference fringes will be ; (a) remain unchanged (b) form closer (c) form further away (d) gradually disappear.
6. Interference of light waves from two coherent sources is possible for ; (a) unpolarised light waves only (b) polarised light waves only if their polarisation is in the same direction (c) both of the above (d) none of the above.
7. Two waves coming from two coherent sources , having different intensity interfere , their ratio of maximum intensity is 25 , then the intensities of the sources are in the ratio ; (a) 25:1 (b) 25:16   (c) 9:4  (d) 5:1 .
8. When petrol drop from a vehicle fall over rain water on the road , colors are seen because of ; (a) dispersion of light (b) scattering of light (c) interference of light (d) absorption of light.
9. In one of the two slits of young’s double slit experiment is painted over so that it transmits half the light intensity of the other , then ; (a) the fringe system will disappear (b) the bright fringe will be more bright (c) the dark fringe will be brighter and vice -versa (d) none of the above .
10. The phenomena of diffraction can be exhibited by ; (a) polarised wave only (b) unpolarised wave only (c) longitudinal wave only (d)all kind of wave
11. Diffraction effects are easily observed for ; (a) microwave (b) sound wave (c) radio waves (d) all of the these .
12. In case of diffraction at single slit if the wavelength of light becomes equal to the aperture of slit , on the screen we shall observe : ; (a) image of slit (b) diffraction band (c)uniform illumination (d) non-uniform illumination.
13. Light of wavelength 2 x 10-3 m falls on a slit of width 4 x 10-3 m . the angular dispersion of the central max will be ; (a) 300 (b) 600 (c) 900 (d) 1800 .
14. The width of the diffraction band varies as (a) inversely as the wavelength (b) directly as the width of the slit (c) directly as the distance between slit and the screen (d) inversely as the size of source from which the slit is illuminated .
15. The polarisation of light prove the ; (a) corpuscular nature of light (b) quantum nature of light (c) transverse wave nature of light (d) longitudinal wave nature of light .
16. A beam of light strikes a piece of glass at an angle of incidence of 600 and reflected beam is completely plane polarized , then the refractive index of glass is  ; (a) 1.5 (b) √3 (c) √2 (d) 2/3.
17. A ray of light incident on the surface of a glass plate at an angle of incidence equal to Brewster’s angle ɸ. If µ is the refractive index of the glass then the angle between reflected and refracted rays is ; (a) (90+ɸ) (b) sin-1 (µ cosɸ) (c) 900 (d) sin-1( sinɸ/µ).
18. A Nicol prism is based on the principle of ; (a) refraction (b) scattering  (c) dichroism (d) double refraction .
19. Which of these wave can be polarised ? (a)sound wave (b) longitudinal wave on a string (c) transverse wave on a string (d) light wave
20. Two Nicol prism are first crossed and ten one of them is rotated through 600 , the percentage of incident light transmitted is ; (a) 1.25 (b)25 (c)37.5 (d)50 .
21. Two polaroids are placed cross to each other , now one of them is rotated through an angle of 450 the percentage of incident light now transmitted through the system is (a)15% (b)25% (c) 50% (d) 60% ( e) 75%.
22. Waves can’t be polarised is ; (a) light wave (b) electromagnetic wave (c) transverse wave (d) longitudinal wave .
23. Young’s double slit experiment is made in a liquid . The tenth bright fringe in the liquid lies where the 6th bright fringe lies in the vacuum . The refractive index of the liquid is approximately ; (a) 1.8 (b) 1.54    (c) 1.67     (d)    2      .
24. If light is polarised by reflection , then the angle between reflected and refracted light is ;  (a) Π     (b) Π/2    (c) Π/3      (d) Π/4
25. A beam of light strikes a piece of glass at an angle of incidence of 600 and the reflected ray is completely polarised . Then the refractive index of the glass is ;  (a) 1.5   (b) √3    (c) √2  (d)3/2
26. What does not change on polarisation of light ;  (a) intensity (b) phase (c) frequency (d) wavelength                                                                                                  TO SOLVE OTHER IMPORTANT QUESTIONS OF WAVE OPTICS – CLOCK HERE