A satellite in earth orbit maintains a panel of solar cells at right angles to the direction of the Sun’s rays. Assuming that solar radiation is monochromatic with a wavelength of 550 nm and arrives at the rate of 1.38 kW, we have to find the area of the panel in order that “one mole of photons” arrives each minute.

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Energy of a 550 nm photon is

Intensity of the solar intensity assuming that the solar radiation is monochromatic with a wavelength of 550 nm is given to be

Therefore, number of photons that will pass per second through plane surface placed at right angles to the Sun’s rays will be

.

And number of photons that will pass through per minute will be

Therefore, the area of the panel through which 1 mol of photons will pass through per minute will be