NEET-XII-Physics
11: Dual Nature Of Radiation And Matter
- #5The 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.
Ans : 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,
Number of photons per square metre incident on earth per second = n
Hence, the equation for power can be written as:
Therefore, every second,
photons are incident per square metre on earth.