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A bulb emits light of wavelength λ=4500A. The bulb is rated as 150 watt and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second?

Option: 1

2 \times 10^{18}


Option: 2

27.2 \times 10^{10}


Option: 3

27.2 \times 10^{18}


Option: 4

54 \times 10^{18}


Answers (1)

best_answer

A 150W bulb emits 150J of energy per second .The energy emitted by the bulb as light is

\begin{array}{l} 150 \times \frac{8}{100}=12 J\\ \text { Let the bulb emit n potons per second }\\ E=n h v=\frac{n h v}{\lambda}\\ \therefore N=\frac{E \times \hat{\lambda}}{c \times h}\\\\ =\frac{12 J \times 45000 \times 10^{-19} m}{3 \times 10^{8} ms ^{-1} \times 6.63 \times 10^{-34} J s}\\\\ =27.15 \times 10^{18} \end{array}

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jitender.kumar

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