Question

Wavelength of a light beam is 25um its wave number is

Answer 1

Answer:

$4 \times {10}^{4}$

Answer 2

Answer:

4×10^2

Explanation:

As we know wave number is reciprocal of wavelength

In this question if we conversation 25 micro metre to cm we get 25×10^-4 and now put it into reciprocal formula.

We get 4×10^2