Dispersion Of Light

Description:

Light is formed by vibrations of electric fields that have a certain frequency. Depending upon the frequency of the light the color of light is determined i.e. different frequency of light have different color.

The velocity of light depends upon frequency of light as well as the wavelength of light, as there are different frequencies in light similarly there are different wavelengths in light.

White light is composed of waves of different wavelengths, different wave-length of light creates different color.

As different colors have different wavelengths, the refractive index of the material of the prism is different for different colors.

As the wavelength of violet light is less than that of red light, the refractive index of the material of the prism for violet light is greater than the refractive index for red light.

Hence, the rays of different colors has different angles of deviation through the prism and they travel in different directions after emerging from the prism. This separation of white light into different colors gives rise to dispersion of light.

The angle of deviation is minimum for red color and maximum for violet color. For other colors the angles of deviation are intermediate between these extreme values.

𝑨𝒏𝒈𝒍𝒆 𝒐𝒇 𝒅𝒊𝒔𝒑𝒆𝒓𝒔𝒊𝒐𝒏 = 𝒂𝒏𝒈𝒍𝒆 𝒐𝒇 𝒅𝒆𝒗𝒊𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒗𝒊𝒐𝒍𝒆𝒕 – 𝒂𝒏𝒈𝒍𝒆 𝒐𝒇 𝒅𝒆𝒗𝒊𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒓𝒆𝒅

Angle of dispersion = δ_v - δ_r

As we known,

δ = A(μ - 1)

∴ Angle of dispersion = A(μ_v - 1) - A(μ_r - 1)

∴ Angle of dispersion = A(μ_v - μ_r)

Dispersive power is the strength of the material to disperse light after refraction. It is given by −

As we have,

Angle of dispersion = δ_v - δ_r

And mean deviation is the average value of deviation of violet and red light. Mean deviation is taken for yellow color while performing experiments in the lab.