Question

Which of the following are responsible for a beam of light being separated into its seven components when it is passed through a prism?
$1$. Total internal reflection
$2$. The index of refraction of prism medium with respect to air varies with wavelength
$3$. The index of refraction of prism medium with respect to air is independent of wavelength
$4$. Velocity of light in prism depends on wavelength.

• A. $1$ and $4$ only
• B. $2$ and $4$ only
• C. $1$ and $2$ only
• D. $2$ and $3$ only

Answer 1

The correct option is B $2$ and $4$ only

Cauchy's formula gives the relation b/w refractive

index of prism medium with wavelength

$n=B+\frac{C}{{\lambda }^2}+\frac{B}{{\lambda }^4}+...$

Also, $v=f\lambda$

Thus, when lights in a prism, it gets separated

into seven different components trawelling with different

velocities