A 100-watt lightbulb radiates energy at a rate of 100 J/s. (The watt, a unit of power, or energy over time, is defined as 1 J/s.) If all of the light emitted has a wavelength of 520nm, how many photons are emitted per second

2.62x10²⁰ photons are emitted per second.

Explanation:

The number of photons emitted per second can be found using the following equation:

  (1)

Where:

h: is the Planck's constant = 6.62x10⁻³⁴ J.s

c: is the speed of light = 3.00x10⁸ m/s

λ: is the wavelength = 520 nm

E: is the energy = 100 J/s

Equation (1) gives the energy for a single photon, so if we have more than one we need to use the term "n" to indicate the number of photons:

By solving the above equation for n we have:

Therefore, 2.62x10²⁰ photons are emitted per second.

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