Question

The radio transmitter operates on a wavelength of $1500m$ at a power of $400kW$. The energy of radio photon (in joule) is:

• A. $1.32\times {10}^{-24}J$
• B. $1.32\times {10}^{-28}J$
• C. $1.32\times {10}^{-26}J$
• D. $1.31\times {10}^{-32}J$

Answer 1

The correct option is B $1.32\times {10}^{-28}J$

Photons are packets of energy (or energy particles) which are emitted by a source of radiation.
According to Planck's quantum theory, a source of radiation emits energy in the form of photons, which travel in straight line.
The energy of photon is
$E=hv=hc/\lambda$
Hence, energy of radio photon is
$E=6.6\times {10}^{-34}\times 2\times {10}^{5}J$

$[\because v=\frac{c}{\lambda }=\frac{3\times {10}^8}{1500}=2\times {10}^{5}Hz]$$\therefore E=1.32\times {10}^{-28}J$