Properties of EM Waves: Practice Problem & Solution
Light with an average flux of $20 W/cm^2$ falls on non-reflecting surface at normal incidence having surface area $20 cm^2$. The energy received by the surface during time span of 1 minute is: (2020)
Short Solution (Best for NEET):
To solve this problem, we apply the core principles of Properties of EM Waves. Understanding the underlying formula is key to arriving at the correct answer below:
Total power received by the surface is $P = Flux \times Area = 20 W/cm^2 \times 20 cm^2 = 400 W$.
The energy received in 1 minute ($60 s$) is $E = P \times t = 400 W \times 60 s$.
$E = 24000 J = 24 \times 10^3 J$.
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