Chapter 5
As a 60kg person walks they apply a 20N force to the surface of the Earth. Recalling that the mass of the Earth is 6x10^24kg, what is the magnitude of the acceleration the Earth experiences from the person walking?
3.3x10^-24 m/s^2
Two stars have the same luminosity, but Star A is 6.0 times farther away than Star B. How much fainter does Star A appear compared to Star B?
36.0 times fainter
What is the rounded value of the speed of light that we will use for this course?
3x10^8 m/s
How does the spectrum of a distant star reveal the star's chemical composition?
Dark lines, also called absorption lines, within the spectra are "fingerprints" for the different atoms and molecules within a star's atmosphere.
Star A and star B appear equally bright in the sky. Star A is twice as far away from Earth as star B. How do the luminosities of stars A and B compare?
Star A is 4 times as luminous as star B.
As a blackbody becomes hotter, it also becomes ______________ and ______________.
more luminous; bluer
When you turn on a lightbulb in a room, the entire room appears to flood with light at the same time. Your eyes cannot perceive light originating at the bulb and then moving outward from it. This either means that light has infinite speed (appears everywhere instantaneously), or it moves so fast that it is difficult to tell the difference. How might you improve your chances of detecting the motion of light if it moves at finite speed?
move farther away from the light source
Based on the information in the previous question what is the magnitude of the acceleration the person experiences?
0.33 m/s^2
Two stars are of equal luminosity. Star A is 3 times as far from you as star B. Star A appears ______________ star B.
1/9 as bright as
What is the surface temperature of a star that has a peak wavelength of 290 nm?
10,000 K
During practice a baseball player applies a force F1 to a weighted baseball of mass m1 which causes an acceleration of a1 on the ball. At the game the player applies triple the force to the standard baseball which has 1/2 the mass of the practice baseball. What is the acceleration of the baseball in the game in terms of a1?
6a1
Why is an iron atom a different element from a sodium atom?
An iron atom has more protons in its nucleus than a sodium atom has.
If the Sun instantaneously stopped giving off light, what would happen on Earth?
Earth would get dark 8 minutes later.
Given that Jupiter has 300 ME and is 5 AU from the sun and Mercury has 1/20 ME and is located at 1/3 AU from the sun, compare the gravitational force between each planet and the sun. Using the equation F = G (m 1 m 2/r 2) which system has the greater gravitational force?
The Jupiter-Sun system
The brightness of an object decreases with increasing distance from the object according to what?
The inverse square law
How does the speed of light in a medium compare with the speed in a vacuum?
The speed in the medium is always slower than the speed in a vacuum.
Scientists discover a planet of 5 ME orbiting a star of 2Ms at a distance of 4AU. How does the gravitational force in this system compare to the Earth-Sun system?
This system has 10/16 the gravitational force of our Earth-Sun system.
When does an equation follow the inverse square law?
When a variable in the denominator is squared.
A light wave does NOT require
a medium in which to propagate
When an electron moves from a higher energy level in an atom to a lower energy level,
a photon is emitted.
When an electron moves from a higher energy level to a lower energy level in an atom,
a photon is emitted.
The average distance of Mars from the Sun is 1.4 AU. How bright is the Sun on Mars compared with its brightness on Earth?
about 2 times fainter
A spectrum that appears dark except for some bright lines is an a ___________. A spectrum that appears to contain the full rainbow except for some dark lines is an ___________.
an emission spectrum, an absorption spectrum
The temperature of an object has a specific meaning as it relates to the object's atoms. A high temperature means that the atoms
are moving very fast.
The "square" in the inverse square law for intensity of light means that
at three times the distance, the intensity is 1/9 as great.
An extremely hot object emits most of its light
at very high energies.
When objects get really hot, they turn
blue
When you look at the sky on a dark night and see stars of different colors, which are the hottest?
blue
If a star is moving towards the earth the spectrum of light observed will appear [shifted].
blue shifted
Hotter stars will appear _______ in the sky while cooler stars will appear ________ in the sky.
blue, red
Light acts like
both a wave and a particle.
The number of electrons in an atom determines what feature of the atom?
charge
As wavelength increases, the energy of a photon __________ and its frequency __________.
decreases; decreases
Which type of wave does NOT need a medium to travel?
electromagnetic waves
When an electron moves from a high energy level to a low energy level a photon is _______. When an electron moves from a low energy level to a high energy level a photon is _______.
emitted, absorbed
Imagine two objects moving away from you. Object A is faster than object B. You will observe that the light
from both objects is redshifted.
From the top down list the categories of electromagnetic waves from highest energy to lowest energy
gamma, visible, radio
In Figure 5.14, the red photons come from the transition from E3 to E2 . Those photons will have the ______________ wave- lengths because they have the ______________energy compared with that of the other photons.
longest; least
Two stars are of equal luminosity. Star A is 3 times as far from you as star B. Star A appears _________ star B.
one-ninth as bright as
What is the name of a particle of light?
photon
When light enters a medium from space it
slows down.
When less energy radiates from a planet, its ______________ increases until a new ______________ is achieved.
temperature; equilibrium
When a boat moves through the water, the waves in front of the boat bunch up, whereas the waves behind the boat spread out. That is an example of
the Doppler effect.
When a boat moves through the water, the waves in front of the boat bunch up, while the waves behind the boat spread out. This is an example of
the Doppler effect.
If a planet is in thermal equilibrium,
the amount of energy leaving equals the amount of energy arriving.
Based on this fact, what can we find from the wavelengths of absorption lines seen in the spectrum of a star?
the composition of any gas between the light-emitting "surface" of the star and the observer
Which of the following factors does not directly influence the temperature of a planet?
the size of the planet
