Wave Optics PYQs Set 1 (PDF)

Set 1 of 10 · Questions 1-30 of 295

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Mere Teacher · Previous Year Questions JEE Main Physics · Wave Optics · Set 1 (Q1-30)
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1. $If a star emitting yellow light is accelerated towards earth, then to an observer on earth it will appear$ (1) $becoming orange$ (2) $shining yellow$ (3) $gradually changing to blue$ (4) $gradually changing to red.$ 2. $A beam of light with intensity 10^{- 3} Nm^{- 2} and cross sectional area 20 cm^{2} is incident on a fully reflective surface at angle 45^{\circ} . Then the force exerted by the beam on the surface is$ (1) $2.3 \times 10^{- 15} N$ (2) $1.33 \times 10^{- 14} N$ (3) $6.67 \times 10^{- 15} N$ (4) $9.4 \times 10^{- 15} N$ 3. $In a double slit experiment the distance between the slits is 0.1 cm and the screen is placed at 50 cm from the slits plane. When one slit is covered with a transparent sheet having thickness and refractive index , the central fringe shifts by 0.2 cm . The value of is cm.$ (1) $5.0 \times 10^{- 3}$ (2) $6.0 \times 10^{- 3}$ (3) $8 \times 10^{- 4}$ (4) $5.6 \times 10^{- 4}$ 4. $In Young's double slit experiment, the wavelength of light used is ' λ'. The intensity at a point is I where path difference is (\frac{λ}{4}) . If I_{0} denotes the maximum intensity, then the ratio (\frac{I}{I _{0}}) is (sin \frac{π}{4} = cos \frac{π}{4} = \frac{1}{2})$ (1) $\frac{1}{2}$ (2) $\frac{1}{2}$ (3) $\frac{3}{4}$ (4) $\frac{3}{2}$ 5. $In a Young s double slit experiment, the ratio of the slit s width is 4 : 1 The ratio of the intensity of maxima to minima, close to the central fringe on the screen, will be:$ (1) $25 : 9$ (2) $9 : 1$ (3) $4 : 1$ (4) $(3+1) 4 : 1 6$ 6. $In a diffraction pattern due to a single slit of width , the first minimum is observed at an angle when light of wavelength is incident on the slit. The first secondary maximum is observed at an angle of$ (1) $sin^{- 1} (\frac{1}{2})$ (2) $sin^{- 1} (\frac{3}{4})$ (3) $sin^{- 1} (\frac{1}{4})$ (4) $sin^{- 1} (\frac{2}{3})$ 7. $A diffraction pattern is obtained by using a beam of red light. If the red light is replaced by the blue light$ (1) $bands will be narrower$ (2) $bands become broader$ (3) $no change in the width of the bands takes place$ (4) $bands disappear$ 8. $For sustained interference fringes in double slit experiment, essential condition/s is/are (1) sources must be coherent. (2) the intensities of the two sources must be equal. Here, the correct option/s is/are$ (1) $both (1) (2)$ (2) $only (1)$ (3) $only (2)$ (4) $neither (1) nor (2)$ 9. $Two monochromatic light waves of amplitudes 3 A and 2 A interfering at a point have a phase difference of 60^{\circ} . The intensity at that point will be proportional to$ (1) $5 A^{2}$ (2) $13 A^{2}$ (3) $7 A^{2}$ (4) $19 A^{2}$ 10. $The fringe width for red colour as compared to that for violet colour is approximately$ (1) $4 times$ (2) $3 times$ (3) $8 times$ (4) $Double$ 11. $For the same angle of incidence, the angles of refraction of media ' ', ' ', ' ' and ' ' are , respectively. The speed of light is minimum in medium$ (1) $P$ (2) $Q$ (3) $R$ (4) $S$ 12. $On using red light (λ = 6600Å) in Young's double slit experiment, 60 fringes are observed in the field of view. If violet light (λ = 4400Å) is used, the number of fringes observed will be$ (1) $30$ (2) $120$ (3) $60$ (4) $90$ 13. $If the polarizing angle of a piece of glass for green light is 54.74^{\circ}, then the angle of minimum deviation for an equilateral prism made of same glass is (Given : tan 54.74^{\circ} = 1.414)$ (1) $45^{\circ}$ (2) $54.74^{\circ}$ (3) $60^{\circ}$ (4) $30^{\circ}$ 14. $In Young's double slit experiment, red light of wavelength 6000Å is used and the n th bright fringe is obtained at a point P on the screen. Keeping the same setting, the source of light is replaced by green light of wavelength 5000Å and now (n + 1) th bright fringe is obtained at the point P on the screen. The value of n is$ (1) $4$ (2) $5$ (3) $6$ (4) $3$ 15. $In Young's double - slit experiment if yellow light is replaced by blue light, the interference fringes become$ (1) $wider$ (2) $brighter$ (3) $narrower$ (4) $darker$ 16. $What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film , wavelength of the light incident on the film .$ (1) $100 nm$ (2) $300 nm$ (3) $50 nm$ (4) $200 nm$ 17. $In an interference pattern of Young's double slit experiment, at a point we observe the 12^{th} order maximum for a monochromatic light source with wavelength 6000Å . What order will be visible here if the source is replaced by a light of wavelength 4800Å ?$ (1) $15$ (2) $10$ (3) $8$ (4) $18$ 18. $In a double slit experiment, when a thin film of thickness having refractive index is introduced in front of one of the slits, the maximum at the centre of the fringe pattern shifts by one fringe width. The value of is is the wavelength of the light used):$ (1) $\frac{2 λ}{( μ - 1 )}$ (2) $\frac{λ}{2 ( μ - 1 )}$ (3) $\frac{λ}{( μ - 1 )}$ (4) $\frac{λ}{( 2 μ - 1 )}$ 19. $A monochromatic light is incident on a single slit of width 0.014 mm . The angular position of the second bright line observed is 2.81^{\circ} . Then the wavelength of the incident light is [(sin (2.81^{\circ}) = 0.049072)$ (1) $4026Å$ (2) $5890Å$ (3) $6040Å$ (4) $2748Å$ 20. $Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion-(A): If Young's double slit experiment is performed in an optically denser medium than air, then the consecutive fringes come closer. Reason-(R): The speed of light reduces in an optically denser medium than air while its frequency does not change. choose the most appropriate answer from the options given below:$ (1) $Both (A) and (R) are true but (R) is not the correct explanation of (A)$ (2) $Both (A) and (R) are true and (R) is the correct explanation of (A)$ (3) $(A) is true but (R) is false$ (4) $(A) is false but (R) is true$ 21. $For what distance is ray optics is good approximation when the aperture is 4 mm and the wavelength of light is 400 nm ?$ (1) $24 m$ (2) $40 m$ (3) $18 m$ (4) $30 m$ 22. $The width of one of the two slits in Young's double slit experiment is d while that of the other slit is x d . If the ratio of the maximum to the minimum intensity in the interference pattern on the screen is 9 : 4 then what is the value of x ? (Assume that the field strength varies according to the slit width.)$ (1) $4$ (2) $5$ (3) $3$ (4) $2$ 23. $In Young's double slit experiment, the ratio of intensities of bright and dark bands is 16 which means$ (1) $the ratio of their amplitudes is 5$ (2) $intensities of individual sources are 25 and 9 units respectively$ (3) $the ratio of their amplitudes is 4$ (4) $intensities of individual sources are 4 and 3 units respectively.$ 24. $For the constructive interference the path difference between the two interfering waves must be equal to$ (1) $(2 n + 1) λ$ (2) $2 nπ$ (3) $nλ$ (4) $(2 n + 1) λ 2$ 25. $A light wave is propagating with plane wave fronts of the type x + y + z = constant. Th angle made by the direction of wave propagation with the x -axis is:$ (1) $cos^{- 1} (2/3)$ (2) $cos^{- 1} (\frac{1}{3})$ (3) $cos^{- 1} (\frac{1}{3})$ (4) $cos^{- 1} (\frac{2}{3})$ 26. $A telescope has large diameter of the objective. Then its resolving power is$ (1) $independent of the diameter of the objective$ (2) $low$ (3) $zero$ (4) $high.$ 27. $A parallel beam of light of wavelength gets diffracted by a single slit of width . The angular position of the first minima of diffracted light is$ (1) $2 \times 10^{- 3} rad$ (2) $3 \times 10^{- 3} rad$ (3) $1.8 \times 10^{- 3} rad$ (4) $6 \times 10^{- 3} rad$ 28. $In a Young's double slit experiment, a laser light of 560 nm produces an interference pattern with consecutive bright fringes' separation of 7.2 mm. Now another light is used to produce an interference pattern with consecutive bright fringes' separation of 8.1 mm. The wavelength of second light is_________nm.$ 29. $Two slits are 1 mm apart and the screen is located 1 m away from the slits. A light of wavelength 500 nm is used. The width of each slit to obtain 10 maxima of the double slit pattern within the central maximum of the single slit pattern is______\times 10^{- 4} m$ 30. $Two waves of intensity ratio 1:9 cross each other at a point. The resultant intensities at the point, when (a) Waves are incoherent is I_{1} (b) Waves are coherent is I_{2} and differ in phase by 60^{\circ} . If \frac{l _{1}}{l _{2}} = \frac{10}{x} then x =______$