# Understanding the Angular Spread of a He-Ne Laser Beam

## What is the minimum angular spread of a 633 nm wavelength He Ne laser beam that is originally 1.00 mm in diameter?

The minimum angular spread of a 633 nm wavelength He Ne laser beam that is originally 1.00 mm in diameter is:

A. 7.72×10⁻⁴ rad

## Answer:

The minimum angular spread of a 633 nm wavelength He Ne laser beam that is originally 1.00 mm in diameter is 7.72×10⁻⁴ rad.

## Explanation:

When dealing with diffraction patterns and the resolution of two light sources, Rayleigh's criterion provides us with a limit of resolution. This criterion states that if the center of one diffraction pattern overlaps with the first minima of the other pattern, the images are just resolvable.

In the case of a He-Ne laser beam with a wavelength of 633 nm and an initial diameter of 1.00 mm, the angular spread can be calculated using Rayleigh's formula:

θ = (1.22)λ/D = 7.72×10⁻⁴ rad

Therefore, the minimum angular spread of the laser beam is 7.72×10⁻⁴ radians.