Question

Light rays are passing from air to glass. Among red, blue, green and violet light, the refractive index of glass will be greatest for- a) Red b) Blue c) Green d) Violet
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Answer 1

Answer:

d)violet

Explanation:

It will be greatest for violet as violet colour has lowest speed and gets refracted the most

Answer 2

Violet will have highest refractive index.

But why ?

• As per Cauchy's Equation, the refractive index for various components of white light is :

$\mu = A + \dfrac{B}{ { \lambda}^{2} } + \dfrac{C}{ { \lambda}^{4} } + ...$

• Neglecting teh higher powers :

$\mu = A + \dfrac{B}{ { \lambda}^{2} }$

• Hence, lower the wavelength of the colour, higher will be the refractive index of the colour.

Violet has the lowest wavelength. Hence, it experiences max refractive index during refraction.