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S R I G A Y A T R I E D U C A T I O N A L I N S T I T U T I O N S - I N D I A

Page | 1 SR MPC JEE MAINS – QUESTION BANK - WAVE OPTICS

SRIGAYATRI EDUCATIONAL INSTITUTIONS INDIA

1. The earth is moving towards a fixed star with a velocity of 130kms . An observer on

the earth observes a shift of 00.58A in the wavelength of light coming from the star.

The actual wavelength of light emitted by the star is 1)

05800A 2) 02400A 3) 012000A 4) 06000A Ans: 1

2. Two beams of light having intensities I and 4I interfere to produce a fringe pattern

on a streen. The phase difference between the beams is / 2 at point A and at point B. Then the difference between the resultant intensities at A and B is

1) 2I 2) 4I 3) 5I 4) 7I

Ans: 2

3. In young’s double slit experiment using monochromatic light of wavelength , the intensity of light at a point on the screen with path difference is M units. The intensity of light at a point where path difference is / 3 , is

1) / 2M 2) / 4m 3) / 8M 4) /16M Ans: 2

4. In young’s double slit experiment, the slits are horizontal. The intersity at a point P

as shown in figure is 0

3 / 4I , where 0

I is the maximum intensity then the value of

is (Give the distance between the two slits 1

S and 2

S is 2

P

1S

2S2

1) 1cos 1/12 2) 1sin 1/12 3) 1tan 1/12 4) 1sin 3 / 5 Ans: 1

5. In young’s double slit experiment, the 10th maximum of wavelength

1 is at a

distance 1

y from its central maximum and the 5th maximum of wavelength 2 is at a

distance 2

y from its central maximum. The ratio 1 2

/y y will be

1) 1

2

2

2) 2

1

2

3) 1

22

4) 2

12

Ans: 1

6. The two slits are 1mm part from each other and illuminated with a light of

wavelength 75 10 m . If the distance of the screen is 1m from the slits, then the

distance between third dark fringe and fifth bright fringe is

1) 1.2mm 2) 0.75mm 3) 1.25mm 4) 0.625mm

Ans: 3

SR MPC JEE MAINS (UT1) – QUESTION BANK WAVE OPTICS



7. In a double slit experiment, the distance between slits is increased ten times whereas

their distance from screen is halved then the fringe width is

1) becomes 1/ 20 2) becomes 1/ 90 3) it remains same 4) becomes 1/10

Ans: 1

8. In a young’s double slit experiment, (slit distanced) monochromatic light of

wavelength is used and the fringe pattern observed at a distance D from the slits. The angular position of the bright fringes are

1) 1sin

N

d

2) 1 1/ 2sinN

d

3) 1sin

N

D

4) 1 1/ 2sinN

D

Ans: 1

9. On introducing a thin film in the path of one of the two interfering beam, the central

fringe will shift by one fringe width. If 1.5 , the thickness of the film is (wavelength of monochromatic light is )

1) 4 2) 3 3) 2 4) Ans: 3

10. A screen is placed 50 cm from a single slit which I illuminated with light of

wavelength 06000A . If the distance between the first and third minima in the

diffraction pattern is 3.0mm. The width of the slit is

1) 41 10 m 2) 42 10 m 3) 40.5 10 m 44 10 m

Ans: 2

11. In single slit diffraction experiment, the width of the slit made double its original

width. Then the central maximum of the diffraction pattern will become

1) narrower and fainter 2) narrower and brighter

3) broader and fainter 4) broader and brighter

Ans: 2

12. In young’s double slit experiment the distanced between the slits 1

S and 2

S is 1mm.

What should the width of each slit be, so as to obtain 10th maxima of the double slit

pattern within the central maximum of the single slit pattern?

1) 0.9 mm 2) 0.8 mm 3) 0.2 mm 4) 0.6 mm

Ans: 3

13. In a fraunhofer diffraction at single slit of width of with d, incident light at

wavelength 05500A , the first minimum is doserved, at angle 030 , the first

secondary maximum is observed at an angle

1) 1 1sin

2

2) 1 1sin

4

3) 1 3sin

4

4) 1 3sin

2

Ans: 3



14. The diameter of the pupil of human eye is about 2mm. Human eye is most sensitive

to the wavelength of 555nm. The limit of resolution of human eye is

1) 1.2 min 2) 2.4 min 3) 0.6 min 4) 0.3 min

Ans: 1

15. A polorid is being used as an analyzer of plane polroid light. In one complete

rotation of the crystal, the maximum intensities will be observed only

1) once 2) twice 3) thrice 4) datu is inadequate

Ans: 2

16. If is the polarising angle for two optical media, whose critical angles are 1

C and

2C . Then the correct relation is

1) 2

1

sinsin

sin

C

C 2) 2

1

sin

sin

C

C 3) 1

2

sintan

sin

C

C 4) 1

2

sinsin

sin

C

C

Ans: 3

17. Unpolarised light of intensity 232Wm passes through three polarisers such that

transmission axis of first is crossed with third. If intensity of emerging light is 22Wm , what is the angle of transmission axis between the first two polarisers?

1) 030 2) 045 3) 022.5 4) 060

Ans: 3

18. Unpolarized light of intensity I is incident on a system of two polarizers, A followed

by B. The intensity of emergent light is 2

I. If a third polarizer C is placed between

A and B. The intensity of emergent light is reduced to 3

I. The angle between the

polarizer A and C is . Then

1)

1/2

1cos

3

2)

1/4

2cos

3

3)

1/2

2cos

3

4)

1/4

1cos

3

Ans: 2

19. In a YDSE arrangement comrposite lights of different wavelengths 1

560nm

and 2

400nm are used. If 1D m , 0.1d mm . The distance (in mm)

between two completely dark regions is

1) 28 2) 18 3) 38 4) 20

Ans: 1

20. The value of numerical aperture of the objective lens of a microscope is 1.25. If

light of wavelength 05000A is used, the minimum separation between two points to

be seen as distinct, will be

1) 0.48 m 2) 0.12 m 3) 0.38 m 4) 0.24 m Ans: 4

21. What speed should a galaxy move with respect to us so that sodium line at

579.0nm is observed at 579.6nm? Ans: 310 /km s



22. Assume that light of wavelength 05000A is coming from a star. What is the limit of

resolution of a telescope whose objective has a diameter of 50 inch?

Ans: 74.8 10 radians

23. In double-slit experiment using light of wavelength 500nm, the Angular width of a

fringe formed on a distant screen is 00.2 . What is the spacing between the two slits?

Ans: 41.4 10 m

24 For what distance is ray optics a good approximation when the aperture is 4mm

wide and the wavelength is 400 nm?

Ans: 40m

25. What should the width of each slit be to obtain 10 maxima of the double slit pattern

within the central maximum of the single slit pattern? 2id d mm Ans: 0.4mm

26. A beam of light consisting of two wavelengths 650nm and 520nm is used to obtain

interference fringes in a young’s double –slit experiment. What is the least distance

from the central maximum where the bright fringes due to both the wavelengths

coincider?

Ans: 1.56mm 27. In a single slit diffraction experiment first minimum for

1660nm coincides

with first maxima for wavelength 2 . The value of

2 (in nm) is

Ans: 440

28. Light of wavelength 06328A is incident normally on a slit of width 0.2mm. The

Angular width of central maximum on a screen (in degree) at distance 9m

is____(Take 3.14 ) Ans: 0.36

29. A system of three polarizers 1 2 3, ,P P P is set up such that the pass axis of

3P is

crossed with respect to that of 1

P . The pass axis of 2

P is inclined at 060 to the pass

axis of 3

P . When a beam of unpolarised light of intensity 0

I is incident on 1

P , the

intensity of light transmitted by the three polarizes is I. The value of 0

/I I equals to

Ans: 10.7

30. The velocity of light in air is 8 13 10 ms and that in water is 8 12.2 10 ms . The

polarising angle of incidence is

Ans: 053.67



Wave Optics (Solutions)

1. V

C

C

V

2. 1I =I 2I =4I

1=2

2=

R 1 2 1 2I =I +I +2 I I cos

AI =I+4I=5I

BI =I+4I-4I=I

A BI -I =4I

3. R 1 2 1 2I =I +I +2 I I cos

Path difference =

Phase difference = 2

2 2. x

.

2

1 2I =I =I

RI =I+I+2 cos2I I

RI =4I M

x=3

2 2=

3 3

R2

I =I+I+2 cos3

I I

RI =I4

M



4. 20I=I cos2

0

I 3=

I 4

2

0

I 3cos =

2 I 4

2 3 3cos cos2 4 2 4

03cos 602 2 3

2x

2

3

x

6x

But path difference

cos 2x d d

2

6 cos

1 1cos

6 2 12

1 1cos12

5. thm m Dy m brightd

11 110 D

y ford

22 25 D

y ford

1 1

2 2

2y

y



6. 75 10 m 1D m

d = 1 m m

thn n Dy n Brightd

55 D

yd

nth

dark 2 1

2n

n Dy

d

3rd

dark 35

2

Dy

d

Distance between 5 3 1.25y y mm

7. D

d

1 1 102

DD d d

1 11

1 2 10 20

D D D

d dd

1

20

8. Path difference sinx d n

1sinbrightN

d

9. Path difference

1x t N

1

3 / 2

N

1

311

2

Nt

2t



10. ; ( )nn D

y d ad

3 1

2(3 1)

D Dy y

a a

3 1

2 Da

y y

11. Angular width of the central maximum is 2

a

12. Angular separation between nth bright fringe nxy n

D d

10th bright 10

10

d

The Angular width of the central maximum in diffraction

1

22

a

10 2

5

da

d a

10.2mm

5a

13. For first secondary minima

sin 1d n n

1

1

sinsin

d d

1( 30)

For secondary maxima

2

3sin

2d

2

3 3sin

2 4d

14. 9

3

555 101.22

2 10d

D D

43.39 10 radd



0 rad 180 0180

1rad =

04 1803.39 10d

1 60

1 2d

15. 20 cosI I

0fI I I

cos 1

0 00 ,180

16. 1 2 ss iin n 90

2

1

Tan

11

1sinc

22

1sinc

1

2

sin

sin

cTan

c

17. 2 20 cos sin2

II

1sin 2

2

02 45

022.5

18. 2cosB cI I

2cos2

cI

I



2 2cos cos2

BI

I

4cos2

BI

I

But 3

BI

I

I

3

I 4cos

2

42 cos3

1/42

cos3

19. nth minima of 400nm coincides with mth minima of 560nm

n my y

400 560(2 1) (2 1)

2 2n m

42 1 7

32 1 5

nn

mm

1(2 1)

142

n Dy mm

d

2(2 1)

422

m Dy mm

d

distance 2 1 28y y mm

20. Numerical aperture of objective lens of microscope 0.61

d

0.61λd=

aperture

0.24d m

21. rad v

c

rad V c



rad 310k / sV m

22. 2 50 Inch a

1Inch 2.54cm

0.61

a

74.8 10 rad

23. 500 nm

oθ = 0.2

θ = dd

4d = 1.4 10 m

24. 2

Fa

Z

40FZ m

25. aa

102

d

102

d a

20.4

5 5

d mma mm

26. 1 1 2 2n n

1 21n n

1 2650 , 520nm nm

5n

The least distance

2n Dxd

1.56x mm



27. sin minimumd n

11sin n = 1d

sin 2 1 max2

d n

22

3sin

2 d

The two will coincide 1 2

2 12

4403

nm

28. 2

a

0.36

29. 012

II

2 2 002 1cos cos 30

2

II I

2

0 02

33

2 2 8

I II

23 2 cosI I

2 00 03

3 3cos 60

8 32

I II

0

3

3210.7

3

I

I

30. C

μ=V

PTan =μ

***

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S R I G A Y A T R I E D U C A T I O N A L I N S T I T U T ... · 03-12-2020 · S R I G A Y A T R I E D U C A T I O N A L I N S T I T U T I O N S - I N D I A Page | 4 SR MPC JEE