# Dispersion through Prisms

## Trending Questions

**Q.**A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of the angle of the prism. The angle of deviation is

- 45∘
- 39∘
- 20∘
- 30∘

**Q.**

What is the difference between Dispersion and Scattering of Light?

**Q.**Which color light has minimum angle of deviation? And why?

**Q.**Prism angle of a prism is 10∘. Refractive index for red and violet colour is 1.51 and 1.52 respectively. Then the dispersive power of the prism is

- 0.019
- 0.011
- 1.515
- 0.029

**Q.**Two prisms A and B have dispersive powers of 0.012 and 0.018 respectively. The two prisms are incontact with each other. The prism A produces a mean deviation of 1.2∘, what is the mean deviation produced by B if the combination is achromatic?

- 0.4∘
- 0.8∘
- 3.6∘
- 1.8∘

**Q.**A plot between the angle of deviation and angle of incidence for a prism is shown in the figure. From the graph one can say that the refracting angle of the prism is :

- 47∘
- 46∘
- 45∘
- 60∘

**Q.**Two prisms A and B are in contact with each other.The dispersive powers of A and B are 0.04 and 0.03 respectively.The angular dispersion produced by A is 8∘. The net angular dispersion produced by the combination, if the combination does not produce a net deviation is

- 14∘
- 8∘
- 6∘
- 2∘

**Q.**White light is passed through a prism of angle 5∘. If the refractive indices for red and violet colours are 1.641 and 1.659 respectively, the angle of dispersion between them is

- 0.090∘
- 3.295∘
- 3.205∘
- None of these

**Q.**The dispersive powers of crown and flint glasses are 0.03 and 0.05 respectively. The refractive indices for yellow light for these glasses are 1.517 and 1.621 respectively. It is desired to form an achromatic combination of prisms of crown and flint glasses which can produce a deviation of 1∘ in the yellow ray. Find the refracting angles of the two prisms needed.

- 4.8∘, 4.8∘
- 2.8∘, 2.4∘
- 4.8∘, 2.8∘
- 4.8∘, 2.4∘

**Q.**Figure shows the graph of angle of deviation δ versus angle of incidence i for a light ray striking a prism. The prism angle is

- 30∘
- 45∘
- 60∘
- 75∘

**Q.**

How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.

**Q.**In a Young’s double-slit experiment, the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in the experiment.

**Q.**A glass prism deviates the red and blue rays through 10∘ and 12∘ respectively. A second prism of equal angle deviates them through 8∘ and 10∘ respectively. Their dispersive powers are in the ratio

- 11: 9
- 9 :11
- 1 : 1
- 3 : 2

**Q.**

In X-ray tube, wavelength of X-ray is the characteristic of :-

tube voltage

target material

filament current

none of these

**Q.**

A thin prism is made of a material having refractive indices 1.61 and 1.65 for red and violet light. The dispersive power of the material is 0.07. It is found that a beam of yellow light passing through the prism suffers a minimum deviation of 4.0∘ in favourable conditions. Calculate the angle of the prism.

**Q.**Flint glass prism is joined by a crown glass prism to produce dispersion without deviation. The refractive indices of these for mean rays are 1.602 and 1.500 respectively. Angle of prism of flint prism is 10

^{o}, then the angle of prism for crown prism will be

- 12∘2.4′
- 12∘4′
- 1.24∘
- 12∘

**Q.**Two prisms A and B have dispersive powers of 0.012 and 0.018 respectively. The two prisms are in contact with each other. The prism A produces a mean deviation of 1.2∘, then the mean deviation produced by B if the combination produces deviation without dispersion is

- 3.6∘
- 0.8∘
- 0.4∘
- 1.8∘

**Q.**

White light is used in a young's double slit experiment. Find the minimum order of the vioet fringe (λ=400nm) which overlaps with a red fringe (λ=700nm.)

**Q.**

A flint glass prism and a crown glass prism are to be combined in such a way that the deviation of the mean ray is zero. The refractive index of flint and crown glasses for the mean ray are 1.620 and 1.518 respectively. If the refracting angle of the flint prism is 6.0∘, what would be the refracting angle of the crown prism ?

**Q.**If a prism of dispersive power 0.021 and refractive index 1.53 forms an achromatic combination with a prism having the prism of angle 4.2∘, dispersive power 0.045 and refractive index 1.65, then what is the resultant deviation of the combination?

- 1.66∘
- 4.12∘
- 4.2∘
- 8.5∘

**Q.**A beam of light has three wavelengths 4144˙A, 4972˙A, 6216˙A with a total intensity of 3.6×10–3W/m2 equally distributed amongst the three wavelengths. The beam falls normally on 1cm2 of a clean metallic surface of work function 2.3eV. The number of photoelectrons liberated in 2 s is closest to (assume every capable photon ejects an electron)

- 8×1011
- 11×1011
- 5×1011
- 2×1011

**Q.**A) Monochromatic light of wavelength 632.8 nm is produced by a helium-neon laser. The power emitted is 9.42 mW .Find the energy and momentum of each photon in the light beam.

B) Monochromatic light of wavelength 632.8 nm is produced by a helium-neon laser. The power emitted is 9.42 mW. How many photons per second, on the average, arrive at a target irradiated by this beam? (Assume the beam to have uniform cross-section which is less than the target area).

C) Monochromatic light of wavelength 632.8 nm is produced by a helium − neon laser. The power emitted is 9.42 mW. How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?"

**Q.**

For the same objective, find the ratio of the least separation between two points to be distinguished by a microscope for light of 5000 A∘ and electrons accelerated through 100 V used as the illuminating substance.

**Q.**In deriving the single slit diffraction pattern, it was stated that the intensity is zero at angles of nλ/a. Justify this by suitably dividing the slit to bring out the cancellation.

**Q.**The prism shown in the figure has a refractive index of 1.60 and angle A as 30∘. Two parallel light rays P and Q enter the prism. The angle between the light rays, when they emerge is:

[Given: sin−1(0.8)=53∘]

- 46∘
- 54∘
- 60∘
- 30∘

**Q.**

Name the factors on which angle of deviation depends.

**Q.**The width of a slit is 0.012mm.monochromatic light is incident on it .the angular position of first bright Line is 5.2 degree.the wavelength of the light incident is

**Q.**The refractive indices of flint glass for red and violet light are 1.613 and 1.632 respectively. Find the angular dispersion produced by a thin prism of flint glass having refracting angle of 5∘.

- 0.081∘
- 0.075∘
- 0.095∘
- 0.06∘

**Q.**A) Answer the following question: In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band?

B) Answer the following question: In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?

C) Answer the following question: When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the center of the shadow of the obstacle. Explain why?

D) Answer the following question: Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily.

E) Answer the following question: Ray optics is based on the assumption that light travels in a straight line. Diffraction effects (observed when light propagates through small apertures/slits or around small obstacles) disprove this assumption. Yet the ray optics assumption is socommonly used in understanding location and several other properties of images in optical instruments. What is the justification?

**Q.**

Explain why images formed by magnifying glasses are free from chromatic aberration