Chapter 6 Telescopes

Question 1

What are the two types of telescopes?

Answer 1

Refracting telescopes and reflecting telescopes

Question 2

How do refracting telescopes work?

Answer 2

Refracting telescopes bend (refract) incoming light through a tube to a focal point.

Question 3

What are the two types of lenses in a refracting telescope?

Answer 3

An objective lens at the front through which light comes through first and an eye piece which magnifies the image.

Question 4

How does a reflecting telescope work?

Answer 4

a reflecting telescope uses mirrors to reflect light to a focal point.

Question 5

What are the mirrors in a reflecting telescope?

Answer 5

A primary mirror is a big curved mirror at the back that starts to focus the light, and the secondary mirror is a smaller mirror at the front that redirects the light towards your eye. There is also an eye piece lens.

Question 6

Which type of telescope is better?

Answer 6

each one has advantages and disadvantages depending on what you want to look at.

Question 7

What do most modern observatories use?

Answer 7

Most modern observatories use reflectors because the telescopes are so huge.

Question 8

What is aperture?

Answer 8

Aperture is the diameter of the opening on the front. The bigger the aperture the more light enters the telescope

Question 9

Why do telescopes need large apertures?

Answer 9

Telescopes need large apertures because the starts only give off dim light, so the aperture needs to be large to let in as much light as possible.

Question 10

What is focal length?

Answer 10

Focal length is the length from the aperture to the focal point in the telescope.

Question 11

What happens as the focal length gets longer?

Answer 11

The longer the focal length the smaller the patch of sky you can see, but the greater the magnification.

Question 12

Why do reflecting telescopes have an advantage when it comes to focal length?

Answer 12

Refractors bend the light down the tube, the tube has to be at least as long as the focal length, but in reflecting telescopes the mirrors reflect the light so the tube can be shorter.

Question 13

What does a telescope do?

Answer 13

A telescope collects light from distant objects using a lens or a concave mirror

Question 14

How does gathering more light help to see distant objects?

Answer 14

Distant objects appear brighter, so then they can be magnified bigger to look closely at them

Question 15

How are simple microscopes and simple refracting telescopes similar?

Answer 15

both have an objective lens and an eye piece lens which bend the light to focus it

Question 16

What does the objective lens do?

Answer 16

the objective lens collects the light and focusses it into an image

Question 17

What does the eye piece lens do?

Answer 17

the image is refracted to the eye piece which then enlarges/magnifies it.

Question 18

What is the focal point in a microscope or telescope?

Answer 18

the focal point is where the light converges

Question 19

What is a problem with refracting telescopes?

Answer 19

to get a detailed image, the objective lens must be large, which makes it heavy and easy to bend the tube

Question 20

What has the weight problem of refracting telescopes meant to inventors?

Answer 20

they had to invent the reflecting telescope.

Question 21

How is a reflecting telescope different?

Answer 21

concave mirror, plane mirror, and a convex lens to collect and focus light

Question 22

Explain the path of light in a reflecting telescope?

Answer 22

light enters, bounces up off a concave mirror, hits an angled plane mirror just before the focal point, then bounces towards the eye piece. The convex lens in the eye piece magnifies the image

Question 23

What does the Keck telescope in Hawaii do?

Answer 23

The Keck has several mirrors so the image is larger.

Question 24

What is the Hubble space telescope?

Answer 24

the Hubble is a telescope that orbits the earth.

Question 25

Why would it be better to look at space from space?

Answer 25

The earth’s environment clouds images, so the image is clear from space

Question 26

What kind of telescope is the Hubble?

Answer 26

the Hubble is a reflecting telescope.

Question 27

How big are the Hubble’s mirrors?

Answer 27

2.4 m across.

Question 28

Does the Hubble only detect light?

Answer 28

No, the Hubble detects electromagnetic radiation as well as light.