Question

What is the wave number for light with a wavelength of 4000 nm?

• A. $2.5\times {10}^{-4}$cm
• B. $5\times {10}^{16}$cm
• C. $7.5\times {10}^4$cm
• D. $8.5\times {10}^4$cm

Answer 1

The correct option is A $2.5\times {10}^{-4}$cm

Ware Number $=\frac{1}{warelength}$

$=\frac{1}{4000}=2.5\times {10}^{-4}cm$

Hence the correct option is A.