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| Why can we recive AM radio waves from far away at night? |
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Definition
| Expansion of the field on the night side by the solar wind raises the ionosphere, so am radio can bounce over long distances. Ionosphere is a good reflector of radio waves. |
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Describe the formation of a star with planets.
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Draw 2 graphs with captions that indicate how astronomers identify exoplanets by the Doppler shift method and the transit method, respectively.
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| What are the two principles of special relativity? |
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Definition
-The laws of physics are the same in all inertial frames of reference
-The velocity of light is the same for all observers
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Describe the effects on space, time and mass that result from these principles, including the mathematical form of the Lorentz factor.
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Definition
For this to be true, an observer measuring a traveling object must observe its:
-space contracted (along the line of travel) -time dilated (slowed), and
-mass increased
all by the same (Lorentz) factor – 1/ 1-(v/c)2
where v is the relative speed of the traveler, and c is the velocity
of light.
(The traveler does not experience these effects for himself.)
(The effects are due to an observed change in the scale of space and time itself.)
(Another result is that mass is a form of energy, E=MC2)
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Term
The Michelson-Morley experiment helped lead to the theory of relativity, What were they attempting to investigate?
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Definition
| Investigating Ether, medium light waves traveled in 1887: doesn't exist, V or light = for all observers |
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Term
Draw a 2-dimensional space-time diagram using the x (horizontal) and time (vertical) dimensions as the axes, of light moving to the right and light moving to the left, passing through x=0 at time t=0.
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A bullet moving directly to the left at roughly half the speed of light bounces off a wall located at x=0 at time t=0, and reflects straight back to the right, still at roughly half the speed of light. Include its path on the diagram with a dotted line (you do not have to correct for the Lorentz factor). (Numbers may be different on the test.)
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Term
Draw a diagram of a star showing and labeling the various layers that astronomers recognize. Indicate which layer is seen as the visible surface, where spectral absorption lines are formed and where hydrogen fusion occurs.
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Term
What is the distance in parsecs to a star of parallax angle 1/100 second of arc? Approximately what is that in light years.
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Term
Draw a diagram illustrating how a basic photoelectric photometer works.
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If a star is 1 parsec away, what is the difference between its absolute magnitude to its apparent magnitude?
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