Question

A standing em wave frequency $2.2\times {10}^{10}Hz$ is produced in a certain material nodal planes of magnetic field are $3.5mm$ apart. Find wavelength and speed of the wave in this material.

• A. $2.81\times {10}^{8}m{s}^{-1}$
• B. $1.79\times {10}^{8}m{s}^{-1}$
• C. $3.08\times {10}^{8}m{s}^{-1}$
• D. $1.54\times {10}^{8}m{s}^{-1}$

Answer 1

The correct option is D $1.54\times {10}^{8}m{s}^{-1}$

Wave length of original wave is equal to twice the wavelength of the standing waves.

$\lambda =2{\lambda }_{st}=2\times 3.5mm=7mm$

Given: $\nu =2.2\times {10}^{10}Hz$

Thus velocity, $v=\nu \lambda =2.2\times {10}^{10}\times 7\times {10}^{-3}$

$⟹v=1.54\times {10}^{8}m/s$