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  • A 50 watt bulb emits monochromatic red light of wavelength of . The number of photons emitted per second by the bulb is <img alt="x \times 10^{20}

A 50 watt bulb emits monochromatic red light of wavelength of 795 \mathrm{~nm}. The number of photons emitted per second by the bulb is x \times 10^{20}. The value of x is ______________.(Nearest integer) [Given : h=6.63 \times 10^{-34}$ Js and $c=3.0 \times 10^{8} \mathrm{~ms}^{-1} ]
 

Answers (1)

best_answer

Given,

Total energy emitted per second \mathrm{= 50\ J}

\begin{aligned} \text { Energy of } 1 \text { photon } &=\frac{h c}{\lambda} \\ &=\frac{6 . 63 \times 10^{-34} \times 3 \times 10^{8}}{795 \times 10^{-9}} \\ &=2 . 5 \times 10^{-19} \end{aligned}

\begin{aligned} \therefore \text { Number of photon } &=\frac{50}{2.5 \times 10^{-19}} \\ &=2 \times 10^{20} \end{aligned}

Hence, the answer is 2 

Posted by

sudhir.kumar

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