Question

The band of colours obtained on a screen on passing white light through a prism is called
(A) Range
(B) Aperture
(C) Spectrum
(D) None of the above.

Answer 1

Prism can be described as transparent solid body. They have three rectangular lateral surfaces and two triangular faces which are inclined to each other at an angle. This angle of inclination is called the angle of prism or refracting angle.
Angle of deviation is defined as the angle between incident ray and emergent ray.
White light is composed of lights having different wavelengths like violet, indigo, green, blue, green, yellow and red. Violet is having the least wavelength and red is having the highest wavelength. So red light is deviated the most while violet light suffers the least deviation.
When white light passes from one optical medium to another, different lights have different angles of deviation because of different wavelengths different colours of light split and this phenomenon of splitting of light is called dispersion.

Complete step by step solution:
When white light is passed through a prism, each colour is deviated which causes the splitting of white light into different components. This phenomenon is called dispersion. Or it can be defined as the splitting of polychromatic light into its constituent colours.
So the band of light obtained on a screen while passing while light through prism is called spectrum.
Correct answer is option C.

Notes:
Refraction: It is a phenomenon in bending the path of the waves.
There are two laws for refraction. The incident ray, the refracted ray and the normal to the interface of two media at the point of incidence all lie on the same plane.
The ratio of sine of angle to incidence to the sine of angle of refraction is a called. This is also known as Snell’s law of refraction
For example the phenomenon of twinkling of stars is due to refraction of light.