Name: __________________________  Date: _____________

1.	The Kelvin scale measures	
A)	temperature in Fahrenheit-sized degrees above absolute zero.	
B)	temperature referenced to zero at the freezing point of water.	
C)	mass per unit volume, or density, with water having a value of 1.0.	
D)	temperature in Celsius-sized degrees above absolute zero.	

2.	To a physicist, a blackbody is defined as an object that	
A)	always emits the same spectrum of light, whatever its temperature.	
B)	reflects all radiation that falls upon it, never heating up and always appearing black.	
C)	always appears to be black, whatever its temperature.	
D)	absorbs all radiation that falls upon it.	

3.	The star Vega has a higher surface temperature than the Sun. If so, then, with IR referring to infrared and UV referring to ultraviolet,	
A)	Vega emits less IR and more UV flux than the Sun.	
B)	Vega emits more IR and more UV flux than the Sun.	
C)	Vega emits more IR and less UV flux than the Sun.	
D)	Vega emits less IR and less UV flux than the Sun.	

4.	Wien's law, relating the peak wavelength max of light emitted by a dense object to its temperature T, can be represented by	
A)	max = constant × T4.	
B)	maxT = constant.	
C)	max = constant/T2.	
D)	max/T = constant.	

5.	Why does the Sun look red when it is setting?	
A)	Red is the Sun's natural color as determined by Wien's law, but it is only when the Sun is close to the horizon that sunlight can pass through the atmosphere unfiltered.	
B)	When the Sun is close to the horizon, it is traveling away from us at great speed, and the Doppler shift makes it look red.	
C)	The Earth's atmosphere scatters longer wavelength light more easily than shorter, so more red light is scattered out of the sunlight and into our eyes.	
D)	The Earth's atmosphere scatters shorter wavelength light more easily than longer, so more red light is left to reach our eyes.	

6.	A spectrograph is a scientific instrument that	
A)	measures the effectiveness of the specular reflection of mirrors.	
B)	spreads out light from a source into its component colors or spectrum.	
C)	measures the transparency of different types of glass at different colors by using glass prisms.	
D)	focuses all the colors of light from a star at one point in order that the total intensity of the star can be measured, for photometry.	

7.	The dark absorption lines in the solar spectrum are caused	
A)	by a cooler layer of gas overlying the hot solar surface, which contains many elements, including hydrogen, helium, magnesium, calcium, iron, etc.	
B)	by a cooler layer overlying the hot solar surface, consisting solely of hydrogen gas, which produces all the absorption lines.	
C)	solely by absorption by atoms and molecules in the Earth' cool atmosphere.	
D)	by a hotter layer of gas that overlies the cooler solar surface and produces the absorption lines.	

8.	An atom consists of	
A)	negatively charged electrons moving around a very small but massive, positively charged nucleus.	
B)	neutrons orbiting an electrically neutral nucleus composed of protons and electrons.	
C)	positive protons, neutral neutrons, and negative electrons, orbiting a small but massive black hole.	
D)	negatively charged electrons and positively charged protons, mixed uniformly throughout the volume of the atom.	

9.	The position of an element in the periodic table, its atomic number, is equal to	
A)	the number of protons in the nucleus of the atom.	
B)	the number of the column in which the element is placed in the periodic table.	
C)	the sum of the number of neutrons and protons in the nucleus of the atom.	
D)	the number of neutrons in the nucleus of the atom.	

10.	Two different isotopes of the element selenium will have	
A)	the same number of protons but a different number of neutrons.	
B)	the same number of protons but a different number of electrons.	
C)	the same number of protons and neutrons, but they are arranged differently in the nucleus.	
D)	the same number of neutrons but a different number of protons.	

11.	O III is	
A)	four-times ionized oxygen (an oxygen atom that has lost four electrons).	
B)	doubly ionized oxygen (an oxygen atom that has lost two electrons).	
C)	an oxygen isotope with three neutrons.	
D)	three-times ionized oxygen (an oxygen atom that has lost three electrons).	

12.	The majority of the mass of ordinary matter resides in	
A)	the electrons and the nuclei, shared about equally.	
B)	the electromagnetic energy stored within the atom, from E = mc2.	
C)	the nuclei of atoms.	
D)	the electron clouds around the nuclei of atoms.	

13.	In Bohr's model of the hydrogen atom, light is emitted whenever	
A)	an electron jumps from a lower to an upper energy level or orbit.	
B)	an electron reverses its direction of motion in its orbit.	
C)	an electron jumps from an upper to a lower energy level or orbit.	
D)	an electron spirals into the nucleus.	

14.	The Balmer series of visible spectral emissions from hydrogen gas arises from transitions in which electrons jump between energy levels	
A)	from all levels to the ground state, n = 1.	
B)	from higher levels to the second excited level, n = 3.	
C)	between adjacent levels (e.g., n = 2 to n = 1, n = 3 to n = 2, n = 4 to n = 3, etc.).	
D)	from higher levels to the first excited level, n = 2.	

15.	The observed change in wavelength of light due to the Doppler effect occurs	
A)	ONLY when the temperature of an object changes.	
B)	ONLY when the light source has proper motion (i.e., motion across the line of sight).	
C)	whenever the light source is moving with respect to the observer (regardless of direction).	
D)	ONLY when the light source has a radial velocity (i.e., motion toward or away from the observer).	

16.	Proper motion is	
A)	the motion of a star or other object across (at right angles to) the line of sight.	
B)	the motion of a star or other object along the line of sight, toward or away from us.	
C)	any motion allowed by the laws of physics.	
D)	the motion of a star or other object in any direction through space.	

17.	The radial velocity of a star or other object is measured by	
A)	measuring the change in the angular diameter of the object.	
B)	watching the object move compared to the background stars.	
C)	measuring the intensity of the light in different regions of the blackbody curve.	
D)	observing the Doppler shift of spectral lines in the light from the object.	

Answer Key

1.	D	
2.	D	
3.	B	
4.	B	
5.	D	
6.	B	
7.	A	
8.	A	
9.	A	
10.	A	
11.	B	
12.	C	
13.	C	
14.	D	
15.	D	
16.	A	
17.	D