Chapter 5

Question 1

What is collecting power in a telescope

Answer 1

It is how big a telescope is and how much light it collects

Question 2

What is focusing power in a telescope

Answer 2

It is how it uses its mirrors and lenses to bend the path of light and create images

Question 3

What is resolving power in a telescope

Answer 3

It is how clear the image is and how many details show

Question 4

How does the size of the telescope affect the image

Answer 4

The size is directly proportional to the light collected, more light collected means a brighter image is shown.

Question 5

What two methods does focusing power use

Answer 5

Refraction and reflection

Question 6

What is refraction

Answer 6

It is the bending of light due to it shifting between one medium to another and changing speed

Question 7

What telescopes are called refractors

Answer 7

Ones that use lenses to collect and focus light

Question 8

What are disadvantages of refractors

Answer 8

Large lenses are extremely expensive, a large lens is only supported in the middle and will sag, dispersion causes images to have colored fringes, many lens materials absorb short-wavelength light

Question 9

What are reflecting telescopes

Answer 9

What astronomers mainly use today, are telescopes that use mirrors to focus the light

Question 10

How do reflecting mirrors work

Answer 10

A secondary mirror may be used to deflect the light through a hole in the primary mirror and focus the light

Question 11

How do astronomers deal with large mirrors in reflecting telescopes

Answer 11

They developed multi-mirror instruments and extremely thin mirrors

Question 12

What are the 3 styles of reflectors

Answer 12

Prime focus, cassegrain focus, and Newtonian focus

Question 13

How does a prime focus reflector work

Answer 13

Light comes in and bounces off the primary mirror into a mounted camera hanging in the middle of the telescope

Question 14

How does a cassegrain focus reflector work

Answer 14

Light comes in and bounces off the primary mirror, and then bounces off again off of a hanging secondary mirror in the middle back to the observer

Question 15

How does a Newtonian reflector work

Answer 15

Light comes in and bounces off the primary mirror, it then hits a diagonal hanging mirror in the middle and into the observers eyes

Question 16

What is diffraction

Answer 16

It is when waves pass through a narrow opening

Question 17

How does diffraction affect how we see an object

Answer 17

A diffracted point source of light appears as a point surrounded by rings of light. EX: the sun

Question 18

What is resolving power and what limits it

Answer 18

Resolving power is the ability for a telescope to gather detail, it is limited by the wave nature of light and its diffraction

Question 19

How can resolution be increased

Answer 19

It can be increased by a larger telescope diameter

Question 20

How can a larger resolution diameter be achieved

Answer 20

By the use of an interferometer which simultaneously combines the observations from two or more widely spaced telescopes

Question 21

What are the 3 ways of detecting light

Answer 21

The human eye, photographic film, electronic detectors

Question 22

What is photographic film

Answer 22

It chemically stores data to increase sensitivity to dim light. Very inefficient as only 4% of photons are recorded

Question 23

What are electronic detectors

Answer 23

Incoming photons strike an array of semiconductor pixels that are connected to a computer. Efficiencies of 75% possible

Question 24

What are the non visible wavelengths and what emits them

Answer 24

Cold gas= emits radio, dust clouds= emit infrared, hot gases= x-rays

Question 25

What are false color images

Answer 25

They are images typically used to depict wavelengths and distributions in non visible observations

Question 26

What are advantages of space based telescopes

Answer 26

Freedom from atmospheric blurring , freedom from atmospheric absorption

Question 27

What are advantages from ground bass telescopes

Answer 27

Larger collecting power, can be easily fixed

Question 28

What is scintillation (twinkling)

Answer 28

It is the refraction of light from stars, it can be caused by temperature and density in pockets of air that are constantly shifting

Question 29

What can improve distorted seeing for telescopes

Answer 29

Adaptive optics that employ a powerful laser correcting scintillation

Question 30

How do computers help telescopes gather data

Answer 30

Solve equations, move telescopes and feed information to detectors, convert data into useful form, creates networks for communication and data exchange