Wave Optics(11th And 12th > Physics ) Questions and answers for exam Preparation

11th And 12th > Physics

WAVE OPTICS MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1.

In Young's double slit experiment, if one of the slit is closed fully, what will be visible on the screen?

A slit-shaped bright spot
A YDSE interference pattern
A diffraction pattern
Nothing will be visible

Discuss Question

Answer: Option C. -> A diffraction pattern
:
C

If one of the slits is closed then YDSE interference fringes are not formed on the screen, so you might be tempted to say 'A slit-shaped bright spot' will be all that you can see on the screen, but no, think about what you just learnt, a fringe pattern is observed due to diffraction from the single slit that is open.

Question 2.

Monochromatic green light of wavelength 5×10^-7 m illuminates a pair of slits 1 mm apart. The separation of bright lines on the interference pattern formed on a screen 2 m away is

0.25 mm
0.1 mm
1.0 mm
0.01 mm

Discuss Question

Answer: Option C. -> 1.0 mm
:
C

Question 3.

In a Young's double slit experiment with wavelength $5890 ˙ A$ , there are 60 fringes in the field of vision How many fringes will be observed in the same field of vision if wavelength used is $5460 ˙ A$ ?

Discuss Question

Answer: Option A. -> 65
:
A

n_{1} λ_{1} = n_{2} λ_{2}

60 \times 5890 = n_{2} 5460

n_{2} = 65

Question 4.

The similarity between the sound waves and light waves is

[KCET 1994]

Both are electromagnetic waves
Both are longitudinal waves
Both have the same speed in a medium
They can produce interference

Discuss Question

Answer: Option D. -> They can produce interference
:
D

Sound wave and light waves both shows interference

Question 5.

$S_{1}, S_{2}$ are two coherent sources of light. P is a point on the screen such that $S_{2} P - S_{1} P$ = 0.01029 cm. Wave length of light used is $6000 ˙ A$ . The order of the fringe formed at P is

172, bright
171, bright
173, dark
172, dark

Discuss Question

Answer: Option D. -> 172, dark
:
D

x = (2 n - 1) \frac{λ}{2}

1029 \times 10^{- 7} = (2 n - 1) \frac{6000 \times 10^{- 10}}{2}

2 \times 171.5 = 2 n - 1

344 = 2 n

n = 172

Question 6.

In an interference pattern $16^{t h}$ order maximum corresponds to 600nm . What order will be visible if 480nm is used in the same position:

Discuss Question

Answer: Option D. -> 20
:
D

n = 16, y = \frac{n λ D}{d} = \frac{n^{'} λ^{'} D}{d}

n λ = n^{'} λ^{'}

\Rightarrow 16 \times 600 = n^{'} \times 480

\Rightarrow n^{'} = 20

Question 7.

A beam of light consisting of two wavelengths 6500 A and 5200 A is used to obtain interference fringes in Young’s double slit experiment. The distance between the slits is 2 mm and the distance between the plane of the slits and the screen is 120 cm. Find the distance of the $10^{t h}$ bright fringe from the central maximum corresponding to shorter wavelength

1.1 mm
2.6 mm
2.8 nm
3.12 mm

Discuss Question

Answer: Option D. -> 3.12 mm
:
D

d = 2 m m . D = 120 c m, λ = 5200 ˙ A

y_{b r i g h t} = \frac{n λ D}{d}

y_{10} = \frac{10 \times 5200 \times 10^{- 10} 1.2}{2 \times 10^{- 3}}

= 52 \times 6 \times 10^{- 5} m = 3.12 m m

y_{10} = \frac{10 λ D}{d}

Question 8.

The distance between two slits is 1.2 mm. If the wavelength of light used is $4800 ˙ A$ and the screen is at a distance of 1 m from the slits, how many fringes are observed on the screen in the space opposite to the slits

Discuss Question

Answer: Option C. -> 3
:
C

y = \frac{d}{2}; y = n β \Rightarrow \frac{d}{2} = n \frac{λ D}{d}

\Rightarrow n = 1.5

∴

the total fringes=3

Question 9.

In a Young's double - slit experience, the slits are 2mm apart and are illuminated with a mixture of two wavelengths $λ_{0} = 750 n m$ and $λ = 900 n m$ . The minimum distance from the common central bright fringe on a screen 2 m away from the slits where a bright fringe from one interference pattern coincides with a bright fringe from the other, is

1.5mm
3 mm
4.5 mm
6 mm

Discuss Question

Answer: Option C. -> 4.5 mm
:
C

y_{0} = n [\frac{D λ}{d}]

and

y_{n}^{'} = n^{'} (\frac{D λ^{'}}{d})

Equating

y_{n}

and

y_{n}^{'}

,we get

\frac{n}{n^{'}} = \frac{λ^{'}}{λ} = \frac{900}{750} = \frac{6}{5}

Hence, the first position at which overlapping occurs is

y_{6} = y_{6} = \frac{6 (2) (750 \times 10^{- 9})}{2 \times 10^{- 3}} = 4.5 m m

Question 10.

In Young’s double slit experiment, the distance between the slits is 0.2 mm and the distance of the screen from the slits is 2 m. If light of wavelength 500 nm is used, find the number of fringes formed between two points separated by 1 cm on the screen.

Discuss Question

Answer: Option B. -> 2
:
B