Chapter 6: SPECTRUM
Diversion, deviation and spectrum
Q 1.
(i) What are the factors on which total deviation produced by a prism when a ray of light is
passed through it depends?
(ii) Name the color of light that is deviated:
(a) Most
(b) Least
(iii) What do you mean by dispersion of light?
(iv) Define spectrum.
(v) Name the surface of prism on which dispersion of light takes place.
(vi) What is the cause of dispersion?
(vii) Draw a neat diagram to show formation of spectrum when white light is passed through
a prism.
(viii) What do you mean by the statement “wavelength is the characteristic of color
irrespective of its origin”?
ANSWERS:
(i) The angle of deviation (i.e., the deviation produced by a prism) depends on the following
four factors:
The angle of incidence (i)
The material of prism (i.e., on refractive index μ)
The angle of prism (A)
The color of wavelength of light used.
(ii) (a) violet (b) red
(iii) The phenomenon of splitting of white light y a prism, into its constituent colors, is known
as dispersion.
(iv) On passing white light through a prism, the band of colors seen on a scree is called the
spectrum.
(v) Dispersion of light takes place on the first surface of the prism.
(vi) The cause of dispersion of white light is the change in the speed of light with
wavelength. When white length enters the first surface of the prism, light of different
colors due to their different speeds in glass, gets deviated through different angles. Light
of violet color is deviated the most and red light is deviated the least. Hence, a
separation of colors (or dispersion) takes place at the first surface of the prism.
Diversion, deviation and spectrum
Q 1.
(i) What are the factors on which total deviation produced by a prism when a ray of light is
passed through it depends?
(ii) Name the color of light that is deviated:
(a) Most
(b) Least
(iii) What do you mean by dispersion of light?
(iv) Define spectrum.
(v) Name the surface of prism on which dispersion of light takes place.
(vi) What is the cause of dispersion?
(vii) Draw a neat diagram to show formation of spectrum when white light is passed through
a prism.
(viii) What do you mean by the statement “wavelength is the characteristic of color
irrespective of its origin”?
ANSWERS:
(i) The angle of deviation (i.e., the deviation produced by a prism) depends on the following
four factors:
The angle of incidence (i)
The material of prism (i.e., on refractive index μ)
The angle of prism (A)
The color of wavelength of light used.
(ii) (a) violet (b) red
(iii) The phenomenon of splitting of white light y a prism, into its constituent colors, is known
as dispersion.
(iv) On passing white light through a prism, the band of colors seen on a scree is called the
spectrum.
(v) Dispersion of light takes place on the first surface of the prism.
(vi) The cause of dispersion of white light is the change in the speed of light with
wavelength. When white length enters the first surface of the prism, light of different
colors due to their different speeds in glass, gets deviated through different angles. Light
of violet color is deviated the most and red light is deviated the least. Hence, a
separation of colors (or dispersion) takes place at the first surface of the prism.
