Chapter 5

Question 1

Why do we need to study light?

Answer 1

Light is the only tool we have for studying the universe

Question 2

What is a disturbance that travels from on point to another?

Answer 2

It’s a wave

Question 3

How did Rømer study the speed of light?

Answer 3

He studied the timing gaps between eclipses of Jupiter’s moons. He studied the time it took light to reach him from the points where earth was closest and farthest from Jupiter. He then calculated earth’s orbital diameter and came up with a predicted time for the light to hit us. He found that the light was consistently hitting us later then the predicted time.

Question 4

Who was the first one to see clear evidence of light traveling at a finite speed?

Answer 4

Rømer

Question 5

What is the speed of light formula?

Answer 5

3 × 10^8 m/s

Question 6

What is a vacuum?

Answer 6

It’s a region of space that lacks matter

Question 7

What is the speed of light in a vacuum?

Answer 7

300,000 km/s

Question 8

How long does it take light to travel between the earth and the moon?

Answer 8

1.3 light-seconds

Question 9

How long does it take light to travel between the earth and the sun?

Answer 9

8 light-minutes

Question 10

How far away is the closest star?

Answer 10

4.37 light-years

Question 11

What is a light-year

Answer 11

The distance traveled by light in a year

Question 12

Is a light-year a measure of time or distance?

Answer 12

Distance

Question 13

What is the amplitude of a wave?

Answer 13

The height of the wave from above its undisturbed position

Question 14

What is the wavelength of a wave?

Answer 14

The distance between one crest and the next

Question 15

What is the frequency of a wave?

Answer 15

The number of crests that pass a certain point each second

Question 16

What is the unit of frequency?

Answer 16

Hertz (Hz)

Question 17

True or False:

Waves with the longest wavelengths have the longest frequencies

Answer 17

False

Question 18

How are the three physical quantities of the speed of light, frequency and wavelength related?

Answer 18

Wavelength = Speed of light/Frequency

Question 19

What is a spectrum?

Answer 19

Light spread out by a wavelength

Question 20

What does wave-particle durability mean?

Answer 20

It means that light is a wave and a particle. It travels like a wave and hits like a particle

Question 21

What has the longest wavelength in the visible light spectrum?

Answer 21

Red light (700nm)

Question 22

What has the shortest wavelength in the visible light?

Answer 22

Violet (350nm)

Question 23

What is the unit used to measure the wavelength of visible light?

Answer 23

Nanometer (nm)

Question 24

What is the visible spectrum?

Answer 24

Roy G. Biv

Question 25

What is the electromagnetic spectrum?

Answer 25

The whole range of different wavelengths of light

Question 26

List the wavelengths in the electromagnetic spectrum from longest to shortest

Answer 26

1. Radio 2. Microwave 3. Infrared 4. Visible 5. UV 6. X-ray 7. Gamma

Question 27

What is the shortest wavelength of light?

Answer 27

Gamma rays

Question 28

What is the longest wavelength of light?

Answer 28

Radio waves

Question 29

As wavelength increases, the energy of a photon ________ and its frequency _______

Answer 29

1. Decreases | 2. Decreases

Question 30

What are photons?

Answer 30

Particles of light

Question 31

What is the period of a wave?

Answer 31

The time it takes to complete one cycle (1/F)

Question 32

What is anything that occupies space and has mass?

Answer 32

Matter

Question 33

Does a neutron have a positive, negative, or no charge?

Answer 33

No charge

Question 34

Does an electron have a positive, negative, or no charge?

Answer 34

Negative

Question 35

What are isotopes?

Answer 35

Atoms with the same number of protons but different number of neutrons

Question 36

What are molecules?

Answer 36

Groups of atoms bound together by shared electrons

Question 37

Why are x-rays harmful?

Answer 37

They can penetrate through the skin and muscle

Question 38

What is the lowest possible energy state of an atom?

Answer 38

Ground state

Question 39

What is the energy stage above ground state?

Answer 39

Excited state

Question 40

Why do different elements display different patters of lines in their spectra?

Answer 40

Each element has a unique set of energy states and therefore a unique set of wavelengths that can emit or absorb radiation

Question 41

What is the Doppler effect?

Answer 41

The change in wavelength of sound or light that is due to the source moving towards or away from the observer

Question 42

What does it mean if a light is redshifted?

Answer 42

It means that the object is moving away from you and the wavelengths are becoming longer

Question 43

What does it mean if a light is blueshifted?

Answer 43

It means that the object is moving towards from you and the wavelengths are becoming shorter

Question 44

What is a blackbody?

Answer 44

An object that absorbs 100% of the radiation that hits it

Question 45

Using Wien's Law, explain the color and amount of light changes that are observed as the temperature of a hot, glowing object increases.

Answer 45

As the object gets hotter the color goes from red to blue. It also emits more light at all wavelengths

Question 46

Why are blackbodies black?

Answer 46

It doesn't reflect radiation, so it appears black

Question 47

Why are astronomers are interested in blackbody radiation?

Answer 47

Stars behave like blackbodies and emit radiation in a spectrum similar to the spectrum of an ideal blackbody.

Question 48

How do electrons move from one orbit to another?

Answer 48

When an atom absorbs a large amount of energy, the electron is no longer bound to the nucleus, and can roam free

Question 49

What are the atoms that have become positively charged by losing one or more electron called?

Answer 49

Ions

Question 50

List the three different types of spectra

Answer 50

1. Continuous spectra 2. Emission spectra 3. Absorption spectra

Question 51

What is the continuous spectra?

Answer 51

A spectrum containing all wavelengths, without specific spectral lines

Question 52

What is the emission spectra?

Answer 52

A series of bright lines with a dark background

Question 53

What is the absorption spectra?

Answer 53

A series of dark lines on a continuous spectrum

Question 54

What does Planck's Law relate?

Answer 54

The energy of the photon to its wavelength of the wave

Question 55

What is the equation for Planck's Law?

Answer 55

E = hc/λ

Question 56

In the equation E = hc/λ, what does each letter represent? 1. E 2. h 3. c 4. λ

Answer 56

1. The energy of a photon 2. Planck's constant 3. The speed of light 4. The wavelength of light

Question 57

What are the four major properties of a wave?

Answer 57

1. Amplitude 2. Wavelength 3. Frequency 4. Speed

Question 58

What is the speed of a wave?

Answer 58

The velocity of a certain point on the wave

Question 59

What are blackbody curves?

Answer 59

They are curves that are apart of the blackbody spectrum, Their shape depends on the temperature

Question 60

Using Stefan-Boltzmann’s Law and Wien's Law, explain the color and amount of light changes that are observed as the temperature of a hot, glowing object increases.

Answer 60

The higher the temperature, the higher the amount of energy that is radiated

Question 61

How can we find the Sun's surface temperature?

Answer 61

By comparing the Sun's spectrum to the appropriate blackbody curve

Question 62

How does intensity of light change with distance?

Answer 62

Brightness decreases as the distance from a light source increases

Question 63

Explain the atomic structure

Answer 63

Atoms have a dense nucleus of protons and neutrons. | Electrons surround the nucleus in a “cloud.”

Question 64

What kind of information can astronomers obtain by studying spectra?

Answer 64

They can find out the chemical composition of the objects

Question 65

What information can one obtain using the Doppler effect?

Answer 65

We can find out if an object in space is moving towards or away from us