Question 1

The energies of two photons you might detect emitted by hydrogen atoms are 10.2 and 2.1 eV. Which photon has the longest wavelength?

Accepted Answer

A)  The 10 eV photon 
B)  They both have the same wavelength. 
C)  The 2.1 eV photon

Question 2

The most common isotope of uranium is U-238, but the form used in nuclear bombs and nuclear power plants is U-235. Given that uranium has atomic number 92, how many neutrons are in each of these two isotopes?

Accepted Answer

The answer of The most common isotope of uranium is...

Question 3

The stars in our sky twinkle in brightness and color because of ________.

Accepted Answer

A)  turbulence in the Earth's atmosphere 
B)  rapid changes in the brightnesses and colors of stars caused by changes in their spectra 
C)  light pollution 
D)  the bubbling and boiling of gases on the surfaces of stars

Question 4

Which of the following statements about X-rays and radio waves is not true?

Accepted Answer

A)  Neither X-rays nor radio waves can penetrate Earth's atmosphere. 
B)  X-rays have shorter wavelengths than radio waves. 
C)  X-rays and radio waves are both forms of light, or electromagnetic radiation. 
D)  X-rays have higher frequency than radio waves. 
E)  X-rays have higher energy than radio waves.

Question 5

Which of the following statements about electrons is not true?

Accepted Answer

A)  Electrons orbit the nucleus rather like planets orbiting the Sun. 
B)  Within an atom, an electron can have only particular energies. 
C)  Electrons can jump between energy levels in an atom only if they receive or give up an amount of energy equal to the difference in energy between the energy levels. 
D)  An electron has a negative electrical charge. 
E)  Electrons have very little mass compared to protons or neutrons.

Question 6

Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?

Accepted Answer

A)  Atomic number = 6; atomic mass number = 13 
B)  Atomic number = 6; atomic mass number = 7 
C)  Atomic number = 13; atomic mass number = 6 
D)  Atomic number = 7; atomic mass number = 13

Question 7

Atomic nuclei consist of protons and electrons.

Accepted Answer

A) True 
 B)False

Question 8

Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?

Accepted Answer

A)  Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons 
B)  Atom 1: nucleus with 6 protons and 8 neutrons, surrounded by 6 electrons; Atom 2: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons 
C)  Atom 1: nucleus with 8 protons and 8 neutrons, surrounded by 8 electrons; Atom 2: nucleus with 8 protons and 8 neutrons, surrounded by 7 electrons 
D)  Atom 1: nucleus with 4 protons and 5 neutrons, surrounded by 4 electrons; Atom 2: nucleus with 5 protons and 5 neutrons, surrounded by 4 electrons

Question 9

Which of the following best describes why we say that light is an electromagnetic wave?

Accepted Answer

A)  The passage of a light wave can cause electrically charged particles to move up and down. 
B)  Light can be produced only by electric or magnetic appliances. 
C)  Light is produced only when massive fields of electric and magnetic energy collide with one another. 
D)  The term electromagnetic wave arose for historical reasons, but we now know that light has nothing to do with either electricity or magnetism.

Question 10

When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called ________.

Accepted Answer

A)  photons 
B)  wavicles 
C)  gamma rays 
D)  frequencies

Question 11

According to the laws of thermal radiation, hotter objects emit photons with ________.

Accepted Answer

A)  a shorter average wavelength 
B)  a lower average frequency 
C)  a lower average energy 
D)  a higher average speed

Question 12

The resolution of a 10-meter telescope is about 0.01 arcsecond for visible light. Would you expect the actual angular resolution of a Keck 10-meter telescope in Hawaii to be better than, equal to, or worse than 0.01 arcsecond? Explain.

Accepted Answer

The answer of The resolution of a 10-meter telescope is...

Question 13

When an electron in an atom goes from a higher energy state to a lower energy state, the atom

Accepted Answer

A)  emits a photon of a specific frequency. 
B)  absorbs a photon of a specific frequency. 
C)  absorbs several photons of a specific frequency. 
D)  can emit a photon of any frequency. 
E)  can absorb a photon of any frequency.

Question 14

There are more atoms in a glass of water than stars in the observable universe.

Accepted Answer

A) True 
 B)False

Question 15

When an atom loses an electron, it becomes

Accepted Answer

A)  sublimated. 
B)  dissociated. 
C)  ionized. 
D)  an isotope. 
E)  a plasma.

Question 16

An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

Accepted Answer

A)  26 protons, 30 neutrons, 26 electrons 
B)  26 protons, 30 neutrons, 30 electrons 
C)  26 protons, 56 neutrons, 26 electrons 
D)  13 protons, 43 neutrons, 13 electrons 
E)  13 protons, 56 neutrons, 13 electrons

Question 17

World Observatories: In order to carry out new observations, modern astronomy requires access to highly specialized telescopes and instruments, be it telescopes in space such as the HST, or large collections of linked radio telescopes like the VLA. These facilities are so expensive to construct and maintain that we are entering an age in which only a single facility for each type of instrument will exist to serve the entire world. What do you think the impact of having only "world observatories" will be on the science of astronomy? Will it influence the scientific process? Should taxpayers be more willing to fund sciences like astronomy in order to avoid this situation?

Accepted Answer

The answer of World Observatories: In order to carry out...

Question 18

Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?

Accepted Answer

A)  Several kilometers 
B)  A few meters 
C)  Several centimeters 
D)  To the Sun

Question 19

Why is the Earth's daytime sky blue?

Accepted Answer

A)  Molecules scatter blue light more than red light. 
B)  The sky reflects the blue of the oceans and lakes. 
C)  Molecules absorb more red light than blue light. 
D)  Air molecules are blue in color.

Exam 5: Light: the Cosmic Messenger