Question

Light of wavelength 5000 Angstrom falls on a sensitive surface.if surface has received 10^-7 J energy.how many photons have fallen on the surface

Answer 1

Answer:25x10^10

Explanation:n=energy flux/ energy of photon

Answer 2

There are $2.49\times 10^{11}\ photons$ have fallen on the surface.

Explanation:

It is given that,

Wavelength of light, $\lambda=5000\ A=5000\times 10^{-10}\ m=5\times 10^{-7}\ m$

Energy received by the surface, $E=10^{-7}\ J$

Let n photons have fallen on the surface. The energy of a photon is given by :

$E=\dfrac{nhc}{\lambda}$

$n=\dfrac{E\lambda}{hc}$

$n=\dfrac{10^{-7}\times 5\times 10^{-7}}{6.67\times 10^{-34}\times 3\times 10^8}$

$n=2.49\times 10^{11}\ photons$

So, there are $2.49\times 10^{11}\ photons$ have fallen on the surface. Hence, this is the required solution.

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Energy of a photon

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