# Worksheet: Telescopes

In this worksheet, we will practice calculating the imaging properties of reflecting, refracting, and compound optical systems used in telescopes.

**Q6: **

A telescope can be used to enlarge the diameter of a laser beam and limit diffraction spreading. The laser beam is sent through the telescope in the direction opposite to the normal one and can then be projected onto a satellite or the Moon. This is done with a telescope, producing a 3.50 m diameter beam of 630 nm wavelength light.

What is the minimum angular spread of the beam produced?

- A rad
- B rad
- C rad
- D rad
- E rad

Neglecting atmospheric effects, find the size of the spot this beam would make on the Moon. Use a value of m for the distance to the Moon.