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# Stuck here, help me understand: The number of photons of light with the wavelength of 4000 pm that provides 1 J of energy is

The number of photons of light with the wavelength of 4000 pm that provides 1 J of energy is

• Option 1)

$2\times10^{16}$

• Option 2)

$1\times10^{18}$

• Option 3)

$3\times10^{15}$

• Option 4)

$3\times10^{16}$

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As learnt in

The energy (E) of a quantum of radiation -

$E=hv$

Where h is plank’s constant and $\nu$ is frequency

-

Thus, $E= nhv$

$\Rightarrow 1 J = n\times 6.62\times 10^{-34}\times \frac{3\times 10^{8}}{4000\times 10^{-12}}$

$\Rightarrow n = 2\times 10^{16}$

Option 1)

$2\times10^{16}$

This solution is correct.

Option 2)

$1\times10^{18}$

This solution is incorrect.

Option 3)

$3\times10^{15}$

This solution is incorrect.

Option 4)

$3\times10^{16}$

This solution is incorrect.

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