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Class 12
Physics
Dual Nature Of Radiation And Matter
the energy flux of sunlight reaching the surface o...

Question:
The energy flux of sunlight reaching the surface of the earth is 1.388 × 10³ W/m². 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.

Answer:

Energy flux of sunlight reaching the surface of earth, Φ = 1.388 × 10³ W/m²

Hence, power of sunlight per square metre, P = 1.388 × 10³ W

Speed of light, c = 3 × 10⁸ m/s

Planck’s constant, h = 6.626 × 10⁻³⁴ Js

Average wavelength of photons present in sunlight, λ = 550 nm = 550 x 10^-9 m

Number of photons per square metre incident on earth per second = n Hence, the equation for power can be written as: P= nE

∴ n = P/E = Pλ / hc = 1.388 x 10³ x 550 x 10^-9 / 6.626 x 10^-34 x 3 x 10⁸ = 3.84 x 10²¹ photons/m²/s

Therefore, every second, 3.84 x 10²¹ photons are incident per square metre on earth.

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Question:
The energy flux of sunlight reaching the surface of the earth is 1.388 × 10³ W/m². 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.

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Question: The energy flux of sunlight reaching the surface of the earth is 1.388 × 103 W/m2. 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.

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Question:
The energy flux of sunlight reaching the surface of the earth is 1.388 × 10³ W/m². 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.