JEE Main 2022 · 26 Jul · Shift 1 · Physics Q34

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PhysicsSingle correct+4 / -1Question 34 of 90

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

3\times10^{16}

4.5\times10^{16}

4.5\times10^{17}

4.5\times10^{20}

Answer and worked solution

Official answer: B

Photon energy $\frac{hc}\lambda=2.2\times10^{-19}$ J; power through 1 cm² is $10^{-2}$ W: $4.5\times10^{16}$ photons s $^{-1}$ .

(B)

Topics:Photon momentum and radiation pressure

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JEE Main 2022 · 26 Jul · Shift 1, Physics question 34