#### Question

What is the number of photons of light with a wavelength of 4000 pm that provide 1 J of energy?

#### Solution

Energy (E) of a photon = hν

Energy (E_{n}) of ‘n’ photons = nhν

`=> n = (E_nlambda)/(hc)`

Where,

λ = wavelength of light = 4000 pm = 4000 ×10^{–12} m

c = velocity of light in vacuum = 3 × 10^{8 }m/s

h = Planck’s constant = 6.626 × 10^{–34} Js

Substituting the values in the given expression of *n:*

`n= ((1)xx(4000xx10^(-12)))/(6.626xx10^(-34)) = 2.012 xx 10^(16)`

Hence, the number of photons with a wavelength of 4000 pm and energy of 1 J are 2.012 × 10^{16}

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Solution What is the Number of Photons of Light with a Wavelength of 4000 Pm that Provide 1 J of Energy? Concept: Particle Nature of Electromagnetic Radiation: Planck'S Quantum Theory.