Physics

Problem

A parallel beam of light of wavelength 900 nm and intensity

100 \text{ Wm}^{-2}

is incident on a surface perpendicular to the beam. The number of photons crossing

1 \text{ cm}^2

area perpendicular to the beam in one second is : [July 26, 2022 (I)] (a)

3 \times 10^{16}

(b)

4.5 \times 10^{16}

(c)

4.5 \times 10^{17}

(d)

4.5 \times 10^{20}