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. $3 \times 10^{16}$
• B. $4.5 \times 10^{16}$
• C. $4.5 \times 10^{17}$
• D. $4.5 \times 10^{20}$

Answer 1

Answer: (B)

$4.5 \times 10^{16}$

Answer 2

The correct option is(B): $4.5 \times 10^{16}$.