Question

for a wave intensity 1 watt/m2 and wavelength 1um in vaccum.find number of photons. Compare this with characteristic thermal energy at 300k

Answer 1

Answer 2

Solution:

The number of photons per second=[Wave intensity/Energy]= [Wave intensity/{hc/}]

Where Wave intensity = 1 W/m², h=6.626x10^-34 Js, c=3x10⁸, and =1um=1x10^-6m

The number of photons per second=[1/{6.626x10^-34 x3x10⁸/1x10^-6}]

=5.03x10¹⁸

The thermal energy at T=300K

We know that, Thermal energy is given by E=kT where k is Boltzmann constant=1.38x10^-23J/K

Thus, E= 1.38x10^-23x 300= 4.14x10^-21 J