Chapter 5 home work 10 Light and Matter Flashcards Preview

Astronomy > Chapter 5 home work 10 Light and Matter > Flashcards

Flashcards in Chapter 5 home work 10 Light and Matter Deck (27):
1

Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?

They have a wavelength of two cycles per second.
We can calculate the wavelength of the ripples from their frequency.
They have a frequency of 2 hertz.
They have a frequency of 4 hertz.

They have a frequency of 2 hertz.

2

Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?

its wavelength and energy
the chemical composition of the object that emitted it
its temperature
its acceleration

its wavelength and energy

3

When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called _________.

frequencies
wavicles
gamma rays
photons

photons

4

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

gamma rays, X rays, ultraviolet, visible light, infrared, radio
infrared, visible light, ultraviolet, X rays, gamma rays, radio
gamma rays, X rays, visible light, ultraviolet, infrared, radio
radio, infrared, visible light, ultraviolet, X rays, gamma rays

gamma rays, X rays, ultraviolet, visible light, infrared, radio

5

Which forms of light are lower in energy and frequency than the light that our eyes can see?

visible light
ultraviolet and X rays
infrared and ultraviolet
infrared and radio

infrared and radio

6

If we say that a material is opaque to ultraviolet light, we mean that it _________.

transmits ultraviolet light
Reflects ultraviolet light
absorbs ultraviolet light
emits ultraviolet light

absorbs ultraviolet light

7

Which of the following transitions within an atom is not possible?

An electron begins in the ground state and then gains enough energy to jump to an excited state.
An electron begins in an excited state and then gains enough energy to jump to the ground state.
An electron begins in an excited state and then gains enough energy to become ionized.
An electron begins in the ground state and then gains enough energy to become ionized.

An electron begins in an excited state and then gains enough energy to jump to the ground state.

8

Thermal radiation is defined as _________.

radiation that is felt as heat
radiation with a spectrum whose shape depends only on the temperature of the emitting object
radiation produced by an extremely hot object
radiation in the form of emission lines from an object

radiation with a spectrum whose shape depends only on the temperature of the emitting object

9

According to the laws of thermal radiation, hotter objects emit photons with _________.

a lower average frequency
a shorter average wavelength
a higher average speed
a lower average energy

a shorter average wavelength

10

Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?

the Doppler shift of the star's spectrum
the peak energy of the star's thermal radiation
the wavelengths of spectral lines in the star's spectrum
whether the star's spectrum has more emission lines or more absorption lines

the wavelengths of spectral lines in the star's spectrum

11

Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien’s law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.

a higher intensity
a shorter wavelength
a longer wavelength

a shorter wavelength

12

Click “show” for the emission line spectrum, then click “choose gases” and study the emission line spectrum for neon. The neon “OPEN” sign appears reddish-orange because __________.

neon atoms emit many more yellow and red photons than blue and violet photons
the yellow and red photons emitted by neon travel much faster than the blue and violet photons and so reach our eyes first
neon atoms emit only yellow and red photons
each yellow and red photon emitted by neon carries more energy than each blue and violet photon emitted.

neon atoms emit many more yellow and red photons than blue and violet photons

13

The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.

appear as a continuous rainbow of colors
be an emission spectrum
appear completely dark
still be an absorption spectrum

be an emission spectrum

14

What type of visible light spectrum does the Sun produce?

a continuous spectrum
an emission line spectrum
an absorption line spectrum

an absorption line spectrum

15

Which of the following statements is true of green grass?

It transmits all colors of light except green.
It absorbs red light and reflects green light.
It absorbs red light and emits green light.

It absorbs red light and reflects green light.

16

Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?

The radio waves from the radio station have a wavelength of 97 million meters.
The "radio waves" received by your radio are not light waves like those we talk about in astronomy, but rather are a special type of sound wave.
The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.
The radio station broadcasts its signal with a power of 97 million watts.

The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second

17

Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength? (Hint: see Mathematical Insight 5.1)

300 million meters
A photon's wavelength cannot be determined from its frequency
1/300,000 meter.
1 meter

1 meter

18

Which of the following statements about X rays and radio waves is not true?

X rays have shorter wavelengths than radio waves.
X rays travel through space faster than radio waves.
X rays have higher frequency than radio waves.
X rays and radio waves are both forms of light, or electromagnetic radiation.

X rays travel through space faster than radio waves.

19

Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?

The cloud is extremely hot.
The cloud is visible primarily because it reflects light from nearby stars.
The cloud is cool and lies between you and a hot star.
The cloud is cool and very dense, so that you cannot see any objects that lie behind it.

The cloud is cool and lies between you and a hot star.

20

Which of the following statements about thermal radiation is always true?

A small hot object produces more total light than a larger, cooler object.
A cold object produces more total infrared and radio emission per unit surface area than a hot object.
All the light emitted by hot object has higher energy than the light emitted by a cooler object.
A hot object emits more radiation per unit surface area than a cool object.

A hot object emits more radiation per unit surface area than a cool object.

21

Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?

It is much more massive than the Sun.
It is much brighter than the Sun.
It is moving away from us.
Its surface is cooler than the surface of the Sun.

Its surface is cooler than the surface of the Sun.

22

What is the wavelength of a radio photon from an "AM" radio station that broadcasts at 820 kilohertz? Remember, 1 kilohertz is the same as 1,000 Hertz.

λ = 370 m

23

What would be the frequency of an electromagnetic wave having a wavelength equal to Earth's diameter?

f = 23.5 Hz

24

In what part of the electromagnetic spectrum would such a wave lie? f = 23.5 Hz

radio
infrared
visible
ultraviolet
X rays
Gamma rays

radio

25

What is the peak wavelength emitted by a person with this temperature? (Hint: what units must you express the temperature in for the laws of Thermal Radiation to work?)

λpeak = 9350 nm

26

In what part of the spectrum does this lie?

radio
infrared
visible
ultraviolet
X rays
Gamma rays

infrared

27

Our sun's surface temperature is approximately 5800 Kelvin. According to the Stefan-Boltzmann law, what is the intensity of light that it is emitting? (Note: Intensity is measured in watts per square meter, or how much energy each square meter of the surface emits every second).

I = 6.42×107 watt/m2