Energy flux of sunlight reaching surface of earth is 1.388 × 10^{3} W / m ^{2} . How many photons (

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11.Dual Nature of Radiation and matter

easy

The energy flux of sunlight reaching the surface of the earth is $1.388 \times 10^{3} \;W / m ^{2} .$ How many photons (nearly) per square metre are incident on the Earth per second? Assume that the photons in the sunlight have an average wavelength of $550\;nm$

A

$9 \times 10^{22}\; Photons / m^{2}\; s$

B

$6\times 10^{22}\; Photons / m^{2}\; s$

C

$8 \times 10^{20}\; Photons / m^{2}\; s$

D

$4 \times 10^{21}\; Photons / m^{2}\; s$

Solution

Energy flux $=1388\, W / m^2$

wavelength $=550\, nm$

Energy of photon $=h c / \lambda$ $=3.61 \times 10^{-19} \,J$

So no. of photons $= P / E$

$=4 \times 10^{21}\; Photons / m^{2}\; s$

Standard 12

Physics

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