Lesson 6

Question 1

How do telescopes work like eyes?

Answer 1

Because they have areas that capture light, as well as focus the light to form images

Question 2

What is refraction? What does it do to light?

Answer 2

The bending of light as it passes from one substance to another
- refraction changes the angle at which light travels

Question 3

What is a focal plane?

Answer 3

Where light from different directions comes into focus

Question 4

What is the focal point?

Answer 4

Where the light from different points can converge

Question 5

What is angular resolution?

Answer 5

The smallest angle over which we can tell that two dots (or two stars) are distinct

Question 6

What is a defraction limit?

Answer 6

The resolution of a telescope that has perfect resolution, save only for the interference of light waves

Question 7

What are the two fundamental properties of telescopes?

Answer 7

1. its light collecting area

2. its angular resolution

Question 8

When a telescope’s light collecting area has a larger diameter, what is the effect produced?

Answer 8

It means that more light is being collected at one time = increases angular resolution

Question 9

What is the angular resolution of the human eye?

Answer 9

approximately 1 degree

Question 10

What is the angular resolution of the Hubble Space telescope?

Answer 10

approximately 0.05 arcseconds

Question 11

What does angular separation depend on?

Answer 11

Actual separation, as well as the distance from us

Question 12

What is the ultimate limit to a telescope’s resolution?

Answer 12

From the interference of light waves in a telescope

Question 13

What does the defraction limit depend on?

Answer 13

The diameter of the telescope, its primary mirror, and the wavelength of light being observed
- larger telescopes have a smaller defraction limit

Question 14

What are the two basic designs of telescopes?

Answer 14

1. refracting telescopes

2. reflecting telescopes

Question 15

Describe refracting telescopes?

Answer 15

They focus the light with lenses, and in order to get a clear picture, the lens needs to be very thick, and the telescope needs to be very long

Question 16

What kind of telescopes are most today?

Answer 16

Reflecting telescopes

Question 17

Describe reflecting telescopes?

Answer 17

They focus light using mirrors

- uses a secondary mirror to reflect light to focus point

Question 18

What are the three subtypes of reflecting telescopes?

Answer 18

a) cassgrain design: light is focused through a hole in the primary mirror
b) newtonian focus: light is focused through a hole in the side of the telescope
c) nasmyth/coude focus- light is focused by a third mirror lower down in the telescope

Question 19

What three things do we use telescopes for?

Answer 19

1. imaging
2. spectroscopy
3. time monitoring (tracks how an object changes with time)

Question 20

Why are most telescopes build at higher altitudes, where the air is thinner?

Answer 20

Because the motion of molecules in earth’s atmosphere distorts images taken by telescopes

Question 21

Which location has one of the largest collections of research telescopes in the world?

Answer 21

Kitt Peak, Arizona

Question 22

Which location is one of the best places for optical telescopes to be built?

Answer 22

Mauna Kea, Hawaii

Question 23

Which location has the most optimal atmospheric conditions for reducing distortion of air particles?

Answer 23

The high deserts in Chile

Question 24

What is another way we can reduce atmospheric distortion?

Answer 24

By putting telescopes in space

Question 25

Why do we need to composite images taken from telescopes in space?

Answer 25

Because they have smaller diameters

Question 26

Why do some telescopes only work in space?

Answer 26

Because certain wavelengths of light can’t penetrate Earth’s atmosphere (i.e. X-rays)

Question 27

What is a radio telescope?

Answer 27

A telescope that reflects radio waves to a focus

Question 28

What are grazing incidence mirrors?

Answer 28

Mirrors specially designed to deflect X-rays

Question 29

What is interferometry?

Answer 29

Allows telescopes to work together, thus adding to their combined angular resolution

Question 30

What two wavelengths most easily pass through Earths’s atmosphere?

Answer 30

• radio waves

- visible light

Question 31

Why might we need more than one type of telescope?

Answer 31

1. Because planets emit primarily infrared light
2. Because hot stars emit ultraviolet light and X-rays
3. Because astronomical events produce gamma rays

Question 32

What is interference?

Answer 32

The place where waves meet

Question 33

Can all telescopes capture light from the visible spectrum?

Answer 33

No

Question 34

Name some non-visible light telescopes

Answer 34

1. Radio telescopes
2. X-ray telescopes
3. gamma ray telescopes

Question 35

Where do X-ray telescopes need to be placed?

Answer 35

Above Earth’s atmosphere, because this wavelength cannot penetrate the atmosphere
- X-ray telescopes need to be specially designed because the X-rays can damage other kinds of telescopes

Question 36

Where do gamma ray telescopes need to be placed?

Answer 36

In space

Question 37

What would happen if a gamma ray hit a regular telescope?

Answer 37

The telescope would be destroyed because of the power of the gamma rays

Question 38

Which kind of telescope would make interferometry easiest to accomplish?

Answer 38

Radio waves;

it is possible to accomplish with with infrared and visible light telescopes as well

Question 39

What are the four categories of robotic space exploration?

Answer 39

1. flyby
2. orbiter
3. sample return mission
4. lander/probe

Question 40

Describe a flyby?

Answer 40

When a spacecraft flies by a planet just once before continuing on its way

Question 41

What does an orbiter space mission accomplish?

Answer 41

It orbits the world it is studying

Question 42

What is a sample return mission?

Answer 42

The robot comes back to Earth to return a sample it has collected

Question 43

What does a lander/probe do?

Answer 43

It either lands on a planet to study it, or to probe an atmosphere