1.

The velocity of all radiowaves in free space is `3xx10^(8),//s`, the frequency of a wave of wavelength `150 m` isA. 20 khzB. 2 kHzC. 2 MHzD. 1 MHz

Answer» Correct Answer - C
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.


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