Question

The number of photons of wavelength 540 nm emitted per second by an electric bulb of power 100W is (taking h = $h=6\times {10}^{-34}J-sec$ )

• A. $100$
• B. $1000$
• C. $3\times {10}^{20}$
• D. $3\times {10}^{18}$

Answer 1

The correct option is C

$3\times {10}^{20}$

$p=\frac{nhc}{\lambda t}\Rightarrow 100=\frac{n\times 6\times {10}^{-34}\times 3\times {10}^8}{540\times {10}^{-9}\times 14}\Rightarrow n=3\times {10}^{20}$