A monochromatic source of light operating at 200W
emits `4 xx 10^20` photons per second. Find the wavelength
of the light.

Explanation

To find the wavelength of the light emitted by a monochromatic source of light operating at 200W that emits \(4 \times 10^{20}\) photons per second, we can follow these steps:

### Step 1: Understand the relationship between power, energy, and photons
The power \(P\) of the light source is given as 200 W, which means it emits 200 joules of energy per second. The energy of a single photon can be expressed using the formula:
\[ E = h \nu \]
where \(E\) is the energy of a photon, \(h\) is Planck's constant (\(6.63 \times 10^{-34} \, \text{J s}\)), and \(\nu\) is the frequency of the light.
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