# Worksheet: Telescopes

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

**Q3: **

A large reflecting telescope has an objective mirror with a 10.0-m radius of curvature. What angular magnification does it produce when a 3.00 m-focal length eyepiece is used?

- A x
- B x
- C x
- D x
- E x

**Q4: **

A planet at a distance of m from Earth is observed by a telescope that has a focal length of the eyepiece of 1 cm and a focal length of the objective of 1 cm. The planet is seen to subtend an angle of rad at the eyepiece. What is the size of the planet?

- A m
- B m
- C m
- D m
- E m

**Q5: **

Two stars that are km apart are viewed by a telescope and found to be separated by an angle of radians . If the eyepiece of the telescope has a focal length of 1.5 cm and the objective has a focal length of 3 meters, how far away are the stars from the observer?

- A km
- B km
- C km
- D km
- E km

**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.

**Q7: **

In a reflecting telescope, the objective is a concave mirror of radius of curvature 4.0 m and the eyepiece is a convex lens of focal length 6.0 cm. Find the apparent size of a 5.0 m tree at 20 km that you would perceive when looking through the telescope.