Assertion `:` Dispersion of light occurs because velocity of light in a material depends upon its colour.
Reason `:` The dispersive power depends only upon the material of the prism, not upon the refracting angle of the prism

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

B

Explanation

The velocity of light in a material medium depends upon it.s colour (wavelength). If a ray of white light incident on a prism, then on emerging, the different colours are deviated through different angles.
Also, dispersive power `omega = ((mu_(V) - mu_(R ) ))/((mu_(Y) - 1))`
i.e., `omega` depends upon only `mu`.