Question

For a certain light there are $2\times {10}^3$ waves in $1.5mm$ in air. The wavelength of light is :

• A. $750nm$
• B. $75A^0$
• C. $750A^0$
• D. $7.5\times {10}^{-7}m$

Answer 1

The correct option is D $7.5\times {10}^{-7}m$

There are $2\times {10}^3$ waves in $1.5mm$ in air which means space occupied by $2\times {10}^3$ waves is $1.5\times {10}^{-3}m$.

So, space occupied by one wave

$=\frac{1.5\times {10}^{-3}}{2\times {10}^3}=0.75\times {10}^{-6}$

$=7.5\times {10}^{-7}m$