• # question_answer The number of photons of wavelength 540 nm emitted per second by an electric bulb of power 100W is (taking h = $6\times {{10}^{-34}}\,J\text{-}sec$) A) 100 B) 1000 C) $3\times {{10}^{20}}$ D) $3\times {{10}^{18}}$

[c]$p=\frac{nhc}{\lambda t}\Rightarrow 100=\frac{n\times 6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{540\times {{10}^{-9}}\times 1}$$\Rightarrow$$n=3\times {{10}^{20}}$