Question

7

Find the energy of the photons for each of the following types of electromagnetic radiation: radio wave of wavelength 80.0 cm; violet light of wavelength 390 nm; X-ray of wavelength o.250 nm

Answer 1

i)

Wave length of radio wave $=\lambda =80cm=0.8m$

Energy of photon $=E$

We know

$E=\frac{hc}{\lambda }$

$h=$ Planck's constant $=6.626\times 10^{-34}J.s$

$c=$ Speed of light $=3\times 10^{8}m/s$

$E=\frac{6.626\times 10^{-34}\times 3\times 10^{8}}{0.8}J=24.85\times 10^{-26}J$

ii)

Wave length of violet light $=\lambda =390nm=390\times 10^{-9}m$

Energy of photon $=E$

We know

$E=\frac{hc}{\lambda }$

$h=$ Planck's constant $=6.626\times 10^{-34}J.s$

$c=$ Speed of light $=3\times 10^{8}m/s$

$E=\frac{6.626\times 10^{-34}\times 3\times 10^{8}}{390\times 10^{-9}}J=50.97\times 10^{-19}J$

iii)

Wave length of X-ray $=\lambda =0.25nm=0.25\times 10^{-9}m$

Energy of photon $=E$

We know

$E=\frac{hc}{\lambda }$

$h=$ Planck's constant $=6.626\times 10^{-34}J.s$

$c=$ Speed of light $=3\times 10^{8}m/s$

$E=\frac{6.626\times 10^{-34}\times 3\times 10^{8}}{0.25\times 10^{-9}}J=79.51\times 10^{-17}J$