The velocity of all radio waves in free space is `3xx10^(8) m//s`. The frequency of a radio wave of wavelength 150 m is:

Options

A. 20 khz
B. 2 kHz
C. 2 MHz
D. 1 MHz

Answer

C

Explanation

As given `E=10cos(10^(7)t+kx)`
Comparing it with standard equation of e.m. wave,
`E=E_(0)cos(omegat+kx)`
Amplitude `E_(0)=10 V//m` and `omega=10^(7) rad//s`
`because c=vlamda=(omegalamda)/(2pi)`
Or `lamda=(2pic)/(omega)=(2pixx3xx10^(8))/(10^(7))=188.4m`
Also,
`c=(omega)/(K)` or `k=(omega)/(c)=(10^(7))/(3xx10^(8))=0.033`
The wave is propagating along y direction.