Question

What is refractive index? Explain.

Answer 1

ANSWER

☆ It is the ratio of the velocity of light in a vacuum to its velocity in a specified medium.

Answer 2

$\huge{ \underline{ \overline{ \mid{ \rm \blue{ANSWER - }} \mid}}}$

$\underline{ \underline{ \rm \pink{Refractive \: Index - }}}$It is measure of the bending of a ray of light when passing from one medium into another.

➡️For all purposes, the speed of light in air as equal to the speed of light in vacuum that is $3 \times {10}^{8} m \: per \: second$

However, in all transparent media, the value of speed of light is less than this. The change in the speed of light on passing from one transparent medium to another depends on their optical densities.

✴️Denser is the medium lesser is the speed of light.

${ \underline{ \bold \red{Types \: Of \: Refractive \: Index - }}}$

1. Relative refractive index

2. Absolute refractive index

$\underline{ \rm{1.Relative \: Refractive \: Index - }}$When the light goes from one medium ( other than vacuum or air) to another medium then that refractive index is called relative refractive index.

➡️If medium 1 is rarer and medium 2 is denser then the speed of light in second medium is less than speed of light in first medium and numerical value of n21 is more than 1. Then,

$\rm{n21 = \frac{speed \: of \: light \: in \: medium \: 1}{speed \: of \: light \: in \: medium \: 2} }$

And, if medium 1 is denser and medium 2 is rarer, then speed of light in second medium is more than speed of light in first medium and numerical value of n12 is less than 1.

$\rm{n12 = \frac{speed \: of \: light \: in \: medium \: 2}{speed \: of \: light \: in \: medium \: 1} }$

$\rm{ \implies \: n2 = \frac{1}{n21} }$

$\underline{ \rm{2. \: Absolute \: Refractive \: Index - }}$Absolute refractive index(nm) of a medium is defined as the ratio of the velocity of light in a vacuum to the velocity of light in the medium.

$\rm{ nm = \frac{speed \: of \: light \: in \: air}{speed \: of \: light \: in \: the \: given \: medium} }$