Question

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

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

Answer 1

The correct option is C $3\times {10}^{20}$

By using $n=\frac{P\lambda }{hc}=\frac{100\times 540\times {10}^{-9}}{6\times {10}^{-34}\times 3\times {10}^8}=3\times {10}^{20}$