Q 12-08-011NEETNEET 2020Top questionEasy
Light with an average flux of $20\ \text{W/cm}^2$ falls on a non-reflecting surface at normal incidence having surface area $20\ \text{cm}^2$. The energy received by the surface during time span of $1$ minute is :
Answer: (C) $24 \times 10^3$ J
Power received: $P = 20\ \text{W/cm}^2 \times 20\ \text{cm}^2 = 400$ W.
$$E = Pt = 400 \times 60 = 24000\ \text{J} = 24 \times 10^3\ \text{J}$$
Solution by Sreeraj P, M.Sc Physics