A parallel beam of light of wavelength 900 nm and intensity 100 Wm -2 is incident on a surface perpendicular to the beam. Tire number of photons crossing 1 cm 2 area perpendicular to the beam in one second is :

Question

A parallel beam of light of wavelength 900 nm and intensity 100 Wm -2 is incident on a surface perpendicular to the beam. Tire number of photons crossing 1 cm 2 area perpendicular to the beam in one second is : (A) 3 × 1016 (B) 4.5 × 1016 (C) 4.5 × 1017 (D) 4.5 × 1020

Tardigrade Admin · Accepted Answer

Wavelength of incident beam λ=900 × 10-9 Intensity of incident beam = I =100 W / m 2 No. of photons crossing per unit sec = n =( E text net / E text single photon )=( IA λ/ hc ) =((100)(1 × 10-4)(900 × 10-9)/6.62 × 10-34 × 3 × 108)=4.5 × 1016

Q. A parallel beam of light of wavelength $900 nm$ and intensity $100 W m^{- 2}$ is incident on a surface perpendicular to the beam. Tire number of photons crossing $1 c m^{2}$ area perpendicular to the beam in one second is :

$3 \times 1 0^{16}$

$4.5 \times 1 0^{16}$

$4.5 \times 1 0^{17}$

$4.5 \times 1 0^{20}$

Q. A parallel beam of light of wavelength 900nm and intensity 100Wm−2 is incident on a surface perpendicular to the beam. Tire number of photons crossing 1cm2 area perpendicular to the beam in one second is :

3×1016

4.5×1016

4.5×1017

4.5×1020

Wavelength of incident beam λ=900×10−9 Intensity of incident beam =I=100W/m2 No. of photons crossing per unit sec =n=Esingle photon ​Enet ​​=hcIAλ​ =6.62×10−34×3×108(100)(1×10−4)(900×10−9)​=4.5×1016

Q. A parallel beam of light of wavelength $900 nm$ and intensity $100 W m^{- 2}$ is incident on a surface perpendicular to the beam. Tire number of photons crossing $1 c m^{2}$ area perpendicular to the beam in one second is :

$3 \times 1 0^{16}$

$4.5 \times 1 0^{16}$

$4.5 \times 1 0^{17}$

$4.5 \times 1 0^{20}$