A helium-neon laser emits red light at wavelength `lambda`=633 nm in a beam of diameter 3.0 mm and at an energy-emission rate of 5.0 mW. A detector in the beam's path totally absorbs the beam. At what rate per unit area does the detector absorb photons?

Explanation

To solve the problem, we need to determine the rate at which the detector absorbs photons per unit area. We will follow these steps:

### Step 1: Calculate the Energy of a Single Photon
The energy of a photon can be calculated using the formula:
\[ E = \frac{hc}{\lambda} \]
where:
...