Question

1. A soap bubble looks colourful under the white illumination. Which of the following statements are TRUE about the phenomena?

A. The refractive index of the bubble is higher than the air.

B. The phenomena is also due to diffraction and reflection of light.

C. The bubble thickness must be 100 times larger than the visible light.

D. If the thickness of the bubble is constant, we can only see one particular colour of the bubble instead of the colourful effect.

2. A thin film coating on a sunglass look reddish when observed under white illumination. The refractive index of the coating is lower than the sunglasses. Which of the following statement are TRUE about the phenomena?

A. The red light is longer in the coating than in the air.

B. The speed of the red light is slower in the coating that in the sunglasses.

C. All colour of light is either partly or completely interfered by the coating except the red light.

D. The relative phase shift between the reflected light from the air-coating interface and the coating-sunglasses is 0

3. Coherent sources Q and R emit electromagnetic waves with wavelength 2 cm. The path difference at P between these two waves is 0.4 cm. The possible distances of P from Q and R are ___ and ___, respectively.

A. 3.2 cm

B. 3.3 cm

C. 3.6 cm

D. 5.6 cm

4. Coherent sources A and B emit electromagnetic waves with wavelength 2.5 cm. The distance between A and B is 5.0 cm. Point P is located somewhere between A and B. Which of the following values are the possible distance of P from A, if it is a point of constructive interference.

A. 1.25 m

B. 2.25 m

C. 3.75 m

D. 4.25 m

5. What effects are responsible for alternating bright and dark fringes formation in the Young‘s Double Slit Experiment?

A. Refraction

B. Diffraction

C. Polarization

D. Interference

6. A beam of white light is made to pass through a narrow single slit. Choose two CORRECT statements about the produced diffraction pattern on a screen at a distance from the slit. A. The centre of the pattern is dark.

B. The centre of the pattern is a bright white.

C. A series of white fringes will be produced on a screen.

D. A series of rainbow-like fringes will be produced on a screen

7. Monochromatic light is incident on a double slit. Bright and dark fringes are formed on a screen. If the intensity is doubled,

A. the fringe separation will be increased.

B. the wavelength will be kept unchanged.

C. the fringe separation will be the same, but the fringes will be brighter.

D. the bright fringes will become wider and the dark fringes will become narrower.

8. A monochromatic light passes through a double slit to produce a pattern on a screen at a distance from the slits. Choose two options to increase the separation between adjacent minima on the screen.

A. Increase the screen-to-slit distance

B. Increase the separation between the slits.

C. Increase the wavelength of the incident light

D. Increase the index of refraction of the medium in which the setup is immersed

9. A monochromatic light passes through a single slit to produce a pattern on a screen at a distance from the slits. Choose two options to increase the separation between adjacent minima on the screen.

A. Increase the screen-to-slit distance

B. Increase the width of the slit.

C. Increase the wavelength of the incident light

D. Increase the index of refraction of the medium in which the setup is immersed

10. A monochromatic light passes through a diffraction grating to produce a pattern on a screen at a distance from the slits. Choose two options to increase the separation between adjacent maxima on the screen.

A. Increase the screen size.

B. Increase the lines per cm of the grating.

C. Increase the wavelength of the incident light

D. Increase the index of refraction of the medium in which the setup is immersed

=One question have 2 answer

Answer 1

1) Ans is A & B

A:The refractive index of the bubble is higher than the air.

B. The phenomena is also due to diffraction and reflection of light.

This phenomenon is called thin film interferance of 2 or more light rays which in turn is generated because of the diffraction and reflection of the light ray falling on the bubble.

2 ) Ans is A & C

A. The red light is longer in the coating than in the air

C:All colour of light is either partly or completely interfered by the coating except the red light.

Sunglasses are coated in such a way that ensures distructive interference of light rays.The relative phase shift between the reflected light from the air-coating interface and the coating-sunglasses will be 180 degree.

3) Ans is A & C

The possible distances of P from Q and R are 3.2 and 3.6, respectively.

4)Ans is A & C

A. 1.25 m

C. 3.75 m

Path difference should be integral multiples of wavelength 2.5 cm.

If P is at 1.25 from A then it will be 3.75 from B.There path difference will be 3.75-1.25=2.5 and vice versa

5) Ans is B & D

Diffraction and Interference

6) Ans is B & C

B. The centre of the pattern is a bright white.

C. A series of white fringes will be produced on a screen

We will get a bright fringe at the center and pattern of alternative bright and dark fringes.But the brightness of all other bright fringes will be very small compared to central fringe.

7) Ans is B & C

B. the wavelength will be kept unchanged.

C. the fringe separation will be the same, but the fringes will be brighter.

Intensity is a measure of brightness of the light.If we increase intensity brightness will increase and wavelength and frequency will remain the same.The width of fringes only depends on the wavelength of the light.So here ther will not be any change in width.

8)Ans is A & C

A. Increase the screen-to-slit distance

C. Increase the wavelength of the incident light

The equation is given by, Fringe Width

is wavelength of light in air

D is distance between screen and slit

n is refractive index of medium

d is distance between slit

So to increase fringe width we have to

a) increase wavelength

b) increase D

c) decrease n

d) Decrease d

9)Ans is A & C

A. Increase the screen-to-slit distance

C. Increase the wavelength of the incident light

To increase seperation between adjacent minima we have to increase fringe width

For central fringe ,Fringe Width   

For all other fringe Fringe Width

10)Ans is B & C

B. Increase the lines per cm of the grating.

C. Increase the wavelength of the incident light

Here we have to note that d=1/N

N is no. of lines per cm

If we increase N ,that will decrease d and so it will increase width ans seperation( By the equation above)