Question 1

A perfect blackbody is so named because it:

Accepted Answer

A)  reflects all radiation falling upon it but emits none of its own. 
B)  absorbs all radiation falling upon it and reflects none. 
C)  never emits radiation. 
D)  always emits the same amount and color of radiation, regardless of its temperature.

Question 2

The hot,dense gas existing on the Sun emits energy:

Accepted Answer

A)  only at certain wavelengths and not at other wavelengths. 
B)  at all wavelengths, with a peak at one particular wavelength (color). 
C)  mostly at the longest and shortest wavelengths, with a minimum in between. 
D)  with the same intensity at all wavelengths. Earth's atmosphere absorbs radiation at both short and long visible wavelengths to produce the observed spectrum.

Question 3

The temperature of boiling water at ordinary air pressure on the absolute scale-Kelvin-is:

Accepted Answer

A)  273 K. 
B)  212 K. 
C)  100 K. 
D)  373 K.

Question 4

If the ground state of the hydrogen atom is taken to be zero energy,then the first three excited states are at energies of 10.2,12.1,and 12.8 eV.The energy corresponding to n = infinity is 13.6 eV.If the atom is in its ground state,it can absorb photons with each of the following energies EXCEPT ONE.Which is the exception?

Accepted Answer

A)  10.2 eV 
B)  12.1 eV 
C)  12.5 eV 
D)  15.2 eV

Question 5

What is chromatic aberration in a telescope?

Accepted Answer

A)  Light of different colors reflecting from the objective mirror of the telescope comes to a focus at different points in front of the mirror. 
B)  Light of different colors comes to a focus at different points behind the objective lens inside the telescope. 
C)  Light striking the lens at different distances from the center of the lens comes to a focus at different points inside the telescope. 
D)  The objective lens varies in thickness from center to edge, and light passing through the different thicknesses suffers different amounts of absorption, thereby coloring the image.

Question 6

A Newtonian telescope uses:

Accepted Answer

A)  only one mirror with its front surface shaped into a parabola. 
B)  one curved mirror and one flat mirror at a 45° angle to the first mirror axis. 
C)  two flat mirrors inclined to each other at a right angle. 
D)  two curved mirrors, one convex, the second concave in shape.

Question 7

The diameter of the nucleus of a typical atom (as measured by Rutherford in the early 1900s)is:

Accepted Answer

A)  10-⁴ of the diameter of the atom. 
B)  10-³ of the diameter of the atom. 
C)  1/2000 of the diameter of the atom. 
D)  about half of that of the atom.

Question 8

Which of the following can travel at the speed of light in a vacuum?

Accepted Answer

A)  light, radio waves, X-rays, and gamma rays 
B)  Only light-all other electromagnetic waves travel slower than the speed of light. 
C)  light, atoms, X-rays, and subatomic particles (e.g., electrons) 
D)  light, infrared radiation, ultraviolet radiation, and subatomic particles (e.g., electrons)

Question 9

If you want to design a device that will detect animals at night by the radiation they emit,even if the night is totally dark,to what wavelength range should you make the device sensitive?

Accepted Answer

A)  ultraviolet 
B)  visual, like the human eye 
C)  No device can detect objects on a totally dark night. 
D)  infrared

Question 10

The series of spectral absorption lines in the infrared part of the spectrum that result from atomic transitions in hydrogen atoms in which electrons are lifted from the n = 3 level to all other atomic energy levels is known as:

Accepted Answer

A)  ionization transitions. 
B)  the Lyman series. 
C)  the Paschen series. 
D)  the Balmer series.

Question 11

One way to distinguish stars from planets,particularly when they appear near the horizon,is that stars appear to twinkle and planets shine steadily.Which of the following statements is a reasonable explanation for this phenomenon?

Accepted Answer

A)  Stars actually do twinkle-shine with a light that flickers bright and dim-whereas planets shine with a steady, unwavering light. 
B)  The light from planets is so much brighter than the light from stars (when they are observed from Earth) that it is unaffected by air movement in Earth's atmosphere. 
C)  The disk of a planet, as observed from Earth, appears larger than the disk of a star. Thus, if refraction through moving air in Earth's atmosphere makes the planet's disk appear to move about slightly, there will normally be a central part of the disk that shines steadily and does not appear to twinkle. 
D)  Because light from planets is reflected, it is unaffected by the refraction in Earth's atmosphere.

Question 12

Consider an atom in which electron transitions can involve three energy levels: highest,middle,and lowest energy.In the resulting bright line spectrum,the line with the shortest wavelength is produced by the transition from:

Accepted Answer

A)  highest to middle. 
B)  highest to lowest. 
C)  lowest to highest. 
D)  middle to lowest.

Question 13

Suppose Rømer had used Saturn and one of its satellites instead of Jupiter and Io to measure the speed of light.How would his measurements have compared with those for Jupiter?

Accepted Answer

A)  The measured time discrepancy between predicted and measured values for a given eclipse would have been shorter for Saturn. 
B)  The measured time discrepancy between predicted and measured values for a given eclipse would have been the same for Saturn. 
C)  The measured time discrepancy between predicted and measured values for a given eclipse would have been longer for Saturn. 
D)  Rømer could not have made such a measurement because Saturn had not yet been discovered.

Question 14

The series of spectral absorption lines in the infrared part of the spectrum,known as the Paschen series,results from atomic transitions in hydrogen atoms in which electrons are lifted from which energy level to all higher atomic energy levels?

Accepted Answer

A)  the n = 1 level, the ground state, because all series start here 
B)  the n = 3 level 
C)  the ionization level 
D)  the n = 2 level

Question 15

If you send white light through a prism to produce a spectrum,and then send the red part of that spectrum through a second prism,the result will be:

Accepted Answer

A)  red. 
B)  yellow. 
C)  white.. 
D)  black (no light).

Question 16

Why was adaptive optics developed?

Accepted Answer

A)  to prevent the distortion of mirrors by the vacuum of space 
B)  to compensate for image distortion caused by Earth's atmosphere 
C)  to compensate for spherical aberration 
D)  to prevent distortion by sagging in very thin, lightweight mirrors

Question 17

The diameter of Earth is about 13,000 km.What distance does light travel in one second,in terms of the diameter of Earth?

Accepted Answer

A)  23 times the diameter 
B)  23,077 times the diameter 
C)  46 times the diameter 
D)  0.043 times the diameter

Question 18

Which of the following elements in the periodic table (see Appendix E of,Discovering the Essential Universe,6th ed.)have chemical properties that are MOST similar to those of nitrogen (N,atomic number 7)?

Accepted Answer

A)  chlorine (Cl, atomic number 17) 
B)  phosphorus (P, atomic number 15) 
C)  carbon (C, atomic number 6) 
D)  oxygen (O, atomic number 8)

Question 19

In which wavelength range does the astronomical satellite known as the Compton Observatory observe?

Accepted Answer

A)  ultraviolet (UV) 
B)  X-ray 
C)  gamma-ray 
D)  infrared (IR)

Question 20

Electromagnetic radiation moving through space with the speed of light consists of oscillating:

Accepted Answer

A)  electric and magnetic fields moving in opposite directions along the same line in space. 
B)  magnetic fields that, over time and distance, change to oscillating electric fields and then back to magnetic fields in a continuous manner. 
C)  electric and magnetic fields, always inseparable, always having the same frequency and wavelength and traveling in the same direction. 
D)  electric fields, with magnetic fields occasionally accompanying them, moving in the same direction.

Exam 3: Light and Telescopes