Light
When an object is moving towards you, is its light that you observe...
a) Redshifted
b) Blueshifted
c) Nothing happens to the light.
d) It depends on the object.
b) Blueshifted
How does the force of gravity Fg change as a function of distance d from a massive object?
a) Fg ~ d
b) Fg ~1/d
c) Fg ~d^2
d) Fg ~ 1/d^2
d) Fg ~ 1/d^2 (inverse square law!)
A changing electric field creates...
a) a magnetic field.
b) electrons.
c) nothing.
d) a bigger electric field.
a) a magnetic field.
What element has only one proton and was formed in Big Bang nucleosynthesis?
a) deuterium
b) hydrogen
c) helium
d) lithium
b) hydrogen
Dark matter is different from dark energy because...
a) dark matter is visible, while dark energy isn't.
b) dark matter makes up more of the universe than dark energy.
c) dark matter is "missing mass" that does not interact with light, while dark energy is the "cosmic anti-gravity" causing the universe's expansion to accelerate.
d) dark matter is explained by the standard model, while dark energy isn't.
c) dark matter is "missing mass" that does not interact with light, while dark energy is the "cosmic anti-gravity" causing the universe's expansion to accelerate.
When a light wave’s energy increases, what happens to its wavelength λ and frequency f?
a) f increases, λ increases
b) f increases, λ decreases
c) f decreases, λ decreases
d) f decreases, λ increases
b) f increases, λ decreases
Newton's theory of gravity is different than Einstein's theory of general relativity because...
a) Only general relativity explains attraction between massive objects.
b) Only Newton's theory explains attraction between massive objects.
c) General relativity explains gravity as the curvature of spacetime by massive objects, so light is bent as a result of gravity, while only massive objects are influenced by gravity in Newton's theory.
d) There isn't any difference.
c) General relativity explains gravity as the curvature of spacetime by massive objects, so light is bent as a result of gravity, while only massive objects are influenced by gravity in Newton's theory.
Accelerating charged particles create...
a) nothing
b) antimatter
c) photons (light)
d) neutrinos
c) photons (light)
What explains why the CMB has approximately the same temperature, even though different parts of it are too far apart to communicate with each other?
a) Dark energy.
b) Cosmic inflation at the start of the universe expanded space faster than the speed of light, spreading apart similar-temperature material that used to be closer together.
c) Information can move faster than the speed of light in the CMB.
d) Dark matter haloes.
b) Cosmic inflation at the start of the universe expanded space faster than the speed of light, spreading apart similar-temperature material that used to be closer together.
Some of the first evidence for dark matter was provided by...
a) seeing spiral galaxies spinning too fast on the edges of their disks for the visible mass they had.
b) measuring that the universe is actually accelerating over time.
c) neutrino measurements.
d) seeing dark matter in the cosmic web.
a) seeing spiral galaxies spinning too fast on the edges of their disks for the visible mass they had.
In the double slit experiment, what is the difference in the way the light behaves when you let it pass through the slits without observing it versus when you do observe it?
a) Light behaves the same whether or not you observe it passing through the slits.
b) When you don't observe it passing through the slits, light behaves as a photon; when you observe it, light behaves as a wave.
c) When you don't observe it passing through the slits, light behaves as a wave; when you observe it, a photon only appears to pass through one slit.
c) When you don't observe it passing through the slits, light behaves as a wave; when you observe it, a photon only appears to pass through one slit.
The escape velocity of a black hole is special because...
a) It is infinite.
b) It is greater than the speed of light.
c) It equals the speed of light.
d) Nothing; the escape velocity is the same as a star of the same mass.
b) It is greater than the speed of light.
What products are produced from a neutron undergoing beta decay?
a) neutron, electron, anti-electron neutrino
b) neutron, positron, neutrino
c) proton, positron, neutrino
d) proton, electron, anti-electron neutrino
d) proton, electron, anti-electron neutrino
The cosmic microwave background is the point when material in the universe...
a) started expanding at a very fast rate.
b) ionized.
c) recombined electrons and protons, making the universe opaque.
d) recombined electrons and protons, allowing light through.
d) recombined electrons and protons, allowing light through.
Which of the following particles could be dark matter?
a) photon
b) neutrino
c) Z-boson
d) none of the above
d) none of the above
When can electrons jump to a higher energy level within an atom?
a) When they absorb a photon with exactly the same energy as the difference between the electron's currently energy level and the higher one.
b) When they absorb any photon.
c) They can just jump up randomly.
d) When they absorb any photon with an energy greater than some specific amount.
a) When they absorb a photon with exactly the same energy as the difference between the electron's currently energy level and the higher one.
Why are galaxies and star systems not ripped apart by dark energy and the expansion of the universe?
a) They are being ripped apart, we just can't see it right now.
b) Gravity is stronger on the scales of galaxies and galaxy clusters so it keeps them together, but the expansion dominates on scales larger than that.
c) Gravity is the strongest force out of all fundamental forces so it keeps everything together.
d) There is no dark energy in our universe.
b) Gravity is stronger on the scales of galaxies and galaxy clusters so it keeps them together, but the expansion dominates on scales larger than that.
The electromagnetic force isn't important on large scales because...
a) Large objects aren't subject to the EM force.
b) The EM force is weak on scales bigger than a proton.
c) Large objects have approximately equal numbers of positive and negative charges, and since they are electrically neutral, the EM force does not impact them.
d) Gravity is a stronger force than the EM force.
c) Large objects have approximately equal numbers of positive and negative charges, and since they are electrically neutral, the EM force does not impact them.
Stars and galaxies formed in regions of the universe that were more dense than others. These regions were originally formed by...
a) dark energy
b) dark matter dragging in dust and gas
c) quantum fluctuations in the very early universe randomly making some parts denser than others
d) stars formed and dragged more gas in with them.
c) quantum fluctuations in the very early universe randomly making some parts denser than others
If we add dark energy to a flat universe, the universe...
a) stays flat, just barely expanding forever.
b) expands at a constant rate.
c) stays the same.
d) accelerates its expansion over time.
d) accelerates its expansion over time.
If I have two stars with the same luminosity, but Star 2 is twice as far away as Star 1, by what amount will the flux received on Earth from the two be different?
a) The flux from Star 2 will be 2x that of Star 1.
b) The flux from Star 2 will be 1/2 that of Star 1.
c) The flux from Star 2 will be 4x that of Star 1.
d) The flux from Star 2 will be 1/4 that of Star 1.
d) The flux from Star 2 will be 1/4 that of Star 1.
Kepler's 3rd law is P^2 = a^3, where P = 1 year and a = 1 AU (distance between the Earth and Sun). If Earth's year were twice as long as it is now, what would its semimajor axis be?
a) a = ∛4 AU
b) a = 4^3 AU
c) a = 1 AU
d) a = 2 AU
a) a = ∛4 AU
Why don't the nuclei of atoms collapse into a black hole or fly apart due to the electromagnetic force?
a) Gravity is stronger than the electromagnetic force and keeps protons and neutrons together so they don't fly apart.
b) They do collapse to a black hole - these are small undetectable black holes.
c) The strong force holding protons & neutrons together is repulsive on small scales but attractive on the scale of protons, and weak at large scales.
d) They inverse beta decay instead of collapsing due to the weak force.
c) The strong force holding protons & neutrons together is repulsive on small scales but attractive on the scale of protons, and weak at large scales.
When stars formed and began to shine, the light from the stars...
a) was absorbed by dark matter around the stars.
b) recombined the hydrogen gas around the stars.
c) ionized the hydrogen gas around the stars.
d) created light visible in the CMB.
c) ionized the hydrogen gas around the stars.
Without the presence of dark energy, what shape of universe and matter density means the universe would freely expand forever?
a) positive curvature ("sphere") / high matter
b) negative curvature ("saddle") / empty
c) flat curvature / high matter
b) flat curvature / critical mass of matter
b) negative curvature ("saddle") / empty