Question

A radio transmitter radiates 1 kW power at a wavelength 198.6 metres. How many photons does it emit per second

• A. ${10}^{10}$
• B. ${10}^{20}$
• C. ${10}^{30}$
• D. ${10}^{40}$

Answer 1

The correct option is C

${10}^{30}$

$P=\frac{W}{t}=\frac{nhc}{\lambda t}\Rightarrow {10}^3=\frac{n\times 6.6\times {10}^{-34}\times 3\times {10}^8}{198.6\times 1}\Rightarrow n={10}^{30}$