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  • A laser emits light with a power of 5.0 mW and a wavelength of 532 nm. What is the total number of photons emitted by the laser in 10 minutes?  Op

A laser emits light with a power of 5.0 mW and a wavelength of 532 nm. What is the total number of photons emitted by the laser in 10 minutes?

 

Option: 1

2.1 \times 10^{20}


Option: 2

3.7 \times 10^{20}


Option: 3

8.04 \times 10^{18}


Option: 4

8.6 \times 10^{20}


Answers (1)

best_answer

The energy of each photon of light emitted by the laser can be calculated using the formula:

\begin{aligned} & E=\frac{h c}{\lambda}=\frac{\left(6.626 \times 10^{-34} \mathrm{~J} \mathrm{~s}\right)\left(3.0 \times 10^8 \mathrm{~m} / \mathrm{s}\right)}{532 \times 10^{-9} \mathrm{~m}} \approx \\ & 3.73 \times 10^{-19} \mathrm{~J} \end{aligned}

The number of photons emitted per second by the laser can be calculated using the formula:

\begin{gathered} n=\frac{P}{E}=\frac{5.0 \times 10^{-3} \mathrm{~W}}{3.73 \times 10^{-19} \mathrm{~J}} \approx 1.34 \times \\ 10^{16} \mathrm{~s}^{-1} \end{gathered}

The total number of photons emitted by the laser in 10 minutes can be calculated by multiplying the number of photons emitted per second by the total number of seconds in 10 minutes:

\begin{gathered} N=n \times t=\left(1.34 \times 10^{16} \mathrm{~s}^{-1}\right) \times \\ (10 \mathrm{~min} \times 60 \mathrm{~s} / \mathrm{min})=8.04 \times 10^{18} \end{gathered}

However, we need to convert the answer to scientific notation to match the given options. Therefore, the total number of photons emitted by the laser in 10 minutes is approximately 8.04 \times 10^{18}, which matches option C.

 

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