The average number of photons emitted per second by a laser of power 6.6 10⁻³ ~W producing a light of wavelength 600 ~nm is (Planck's constant, h=6.6 10⁻³⁴ ~J - s )

Step-by-step solution

Photons emitted per second n= Power Energy of 1 photon = P ( h c ) = P h c Note h c=1240 eV - nm 1 eV =1.6 10⁻¹⁹ ~J As given that, =600 ~nm so, h c = 1240 eV - nm 600 ~nm aligned & =2.067 eV & =2.067 1.6 10⁻¹⁹ ~J =3.3 10⁻¹⁹ ~J aligned So, number of photons / sec =n= P ( h c ) = 6.6 10⁻³ 3.3 10⁻¹⁹ =2 10¹⁶ photons per second.