ch.4

Question 1

What is the speed of light in a vacuum?

Answer 1

299,792.458 km/s

This speed is denoted by the letter ‘c’.

Question 2

What does the term ‘wave-particle duality’ refer to?

Answer 2

Particles of nature behave as both a wave and a particle.

Question 3

What is the visible spectrum?

Answer 3

Colors to which the human eye is sensitive.

Question 4

What unit is used to measure wavelengths in the electromagnetic spectrum?

Answer 4

Nanometer (10^-9 m).

Question 5

What is the relationship between wavelength and frequency?

Answer 5

Frequency (n) is inversely proportional to wavelength (l) as given by nl = c.

Question 6

What is white light composed of?

Answer 6

A mixture of all colors.

Question 7

Who discovered infrared radiation?

Answer 7

Sir William Herschel.

Question 8

What is the primary effect of ultraviolet light?

Answer 8

Responsible for suntans and burns.

Question 9

What did Roentgen discover in 1895?

Answer 9

X-rays.

Question 10

What is the energy carried by a photon given by?

Answer 10

E = hc/l.

Question 11

What is the Kelvin temperature scale related to?

Answer 11

An object’s energy content and speed of molecular motion.

Question 12

What is Wien’s Law?

Answer 12

Peak wavelength is inversely proportional to temperature.

Question 13

What is a blackbody?

Answer 13

An object that absorbs all radiation falling on it.

Question 14

How are electron orbits described in an atom?

Answer 14

Quantized, meaning they can only have discrete values.

Question 15

What happens to an atom’s energy when an electron moves to an outer orbit?

Answer 15

The atom’s energy is increased and is said to be excited.

Question 16

What is spectroscopy used for?

Answer 16

Determining the composition and conditions of an astronomical body.

Question 17

What are the three types of spectra?

Answer 17

• Continuous spectrum
• Emission-line spectrum
• Dark-line (absorption-line) spectrum

Question 18

What is redshift?

Answer 18

An observed increase in wavelength.

Question 19

What phenomenon occurs when an electron in an atom jumps to a higher energy orbital?

Answer 19

Excitation.

Question 20

What is the Doppler Shift equation?

Answer 20

v/c = Δl/l0.

Question 21

What type of electromagnetic radiation reaches the surface of the Earth?

Answer 21

• Visible light
• Radio waves

Question 22

What happens to spectral lines if a light source is moving towards you?

Answer 22

The spectral lines are shorter in wavelength.

Question 23

What is an atmospheric window?

Answer 23

A range of wavelengths of electromagnetic radiation which transmit through the Earth’s atmosphere.

Question 24

What is the relationship between wavelength and energy of a photon?

Answer 24

Short wavelength = high energy; long wavelength = low energy.

Question 25

What is the typical size of an atom?

Answer 25

10^-10 m (= 1 Å = 0.1 nm).

Question 26

What is the conservation of energy in relation to atomic energy changes?

Answer 26

Energy change of an atom must be compensated elsewhere.

Question 27

What is the significance of the number of protons in an element?

Answer 27

It determines the chemical properties of the element.

Question 28

What is the effect of temperature on the radiation emitted by a heated body?

Answer 28

Hotter bodies radiate more strongly at shorter wavelengths.

Question 29

What is an emission spectrum?

Answer 29

A spectrum with bright lines on a dark background.

Question 30

What is an absorption spectrum?

Answer 30

A spectrum with dark lines on a continuous background.

Question 31

What does it mean when a star is approaching you with the speed of 3000 km/s?

Answer 31

The star is moving closer to Earth.

Question 32

What is an atmospheric window?

Answer 32

A range of wavelengths of electromagnetic radiation which transmit through the Earth's atmosphere ## Footnote It allows certain wavelengths to pass while blocking others.

Question 33

Which of the following can be determined from Wien's law?

Answer 33

Only A and C are correct: *The temperature of the surface of the Sun* and *The temperature of a hot tenuous gas*.

Question 34

What determines the identity of a chemical element?

Answer 34

The number of protons in the nucleus.

Question 35

What conclusion can we draw about the motion of a star that does not show any Doppler shift in its spectrum?

Answer 35

The star may be moving perpendicular to our line of sight.

Question 36

What happens when an electron in an atom absorbs a photon?

Answer 36

The electron moves to a higher energy level.

Question 37

What conclusion can be drawn from the position shifts of the Alpha and Beta stars?

Answer 37

The shifts in direction do not provide information on the speed along the line of sight.

Question 38

What is true about the energy change producing spectral lines at different wavelengths?

Answer 38

The energy change producing the 100 nm line is 10 times larger than the change producing the 1000 nm line.

Question 39

Wien's law applies to a _______ spectrum.

Answer 39

Continuous emission.

Question 40

Spectral lines shifted toward higher frequencies are called _____.

Answer 40

Blue-shifted.

Question 41

A ____ is a particle of light.

Answer 41

Photon.

Question 42

The spectral lines of a star will appear ________ if the star is moving away from the Earth.

Answer 42

Red-shifted (i.e., shifted toward the longer wavelengths).

Question 43

______ attraction holds the electron in orbit around the nucleus of the hydrogen atom.

Answer 43

Electrical.

Question 44

The helium atom has ____ in its nucleus.

Answer 44

Two protons.

Question 45

A photon of blue light has ____ a photon of red light.

Answer 45

More energy than.

Question 46

When a spectral line of hydrogen appears at 662 nm instead of 656 nm, what can we conclude?

Answer 46

D. Is moving away from us at about 1% the speed of light.

Question 47

An oxygen atom that loses 1 electron becomes

Answer 47

A positively charged ion.

Question 48

A night vision camera uses a detector sensitive to _______ light.

Answer 48

Infrared.

Question 49

Conservation of energy requires that if an atom absorbs a photon,

Answer 49

An electron rises to a new orbital with an energy equal to that of the previous orbital plus the energy of the photon.

Question 50

A temperature of 0 Kelvin means there is essentially no motion at the atomic level. True or False?

Answer 50

True.

Question 51

A piece of iron heated to 200 degrees Celsius has twice as much internal energy as a piece of iron at 100 degrees Celsius. True or False?

Answer 51

False.

Question 52

The Doppler shift is the same if the emitting object is moving towards you at some speed, or you are moving towards it at that speed and it is still. True or False?

Answer 52

True.

Question 53

An atom with 3 protons and 3 neutrons is a lithium atom, and an atom with 3 protons and 4 neutrons is also a lithium atom. True or False?

Answer 53

False.

Question 54

Electrons orbit the nucleus in just the same way that planets orbit the Sun. True or False?

Answer 54

False.

Question 55

If you add more hydrogen to a jar filled with hydrogen, the position of spectral lines will change. True or False?

Answer 55

False.

Question 56

The Doppler shift applies only to the line spectrum. It does not apply to the continuous (blackbody) spectrum. True or False?

Answer 56

False.

Question 57

A continuous blackbody emission spectrum provides information about the surface temperature of the object. True or False?

Answer 57

True.

Question 58

The continuous blackbody emission spectrum provides a 'signature' of the chemical composition of the object. True or False?

Answer 58

False.

Question 59

In space, X-rays travel faster than radiowaves. True or False?

Answer 59

False.

Question 60

Scientists use the term 'blackbody' to indicate a surface that will not emit any color of visible light. True or False?

Answer 60

False.

Question 61

The higher the frequency of the electromagnetic wave, the shorter its wavelength. True or False?

Answer 61

True.

Question 62

According to Wien's law, the dominant wavelength in the continuous emission spectrum of a red apple is 700 nm. True or False?

Answer 62

True.

Question 63

Cooler stars (about 3000 K) emit most of their radiation at wavelengths shorter than 600 nm. True or False?

Answer 63

False.

Question 64

The chemical composition of a gas can be determined by analysis of the spectral lines of the gas. True or False?

Answer 64

True.

Question 65

When an atom absorbs energy it becomes excited. True or False?

Answer 65

True.

Question 66

When an atom emits light, an electron in it moves from a higher to a lower energy level. True or False?

Answer 66

True.

Question 67

The color of a yellow banana is a result of blackbody emission. True or False?

Answer 67

False.

Question 68

The spectral lines from a star that is moving away from the Earth will appear redshifted. True or False?

Answer 68

True.