Chapter 11

14. What is the only force that can overcome the repulsion between two positively charged nuclei to bind them into an atomic nucleus? A) the strong force B) the weak force C) the electromagnetic force D) the gravitational force E) the Coriolis force

A

16. Which of the following is not a method astronomers use to determine the physical conditions inside the Sun? A) observing X-ray images of the solar interior using satellites B) building mathematical models that use the laws of physics C) detecting solar neutrinos generated in the Sun's core D) measuring Doppler shifts to observe solar vibrations E) both C and D

A

19. Approximately how many neutrinos pass through your body each second? A) about a thousand trillion B) about one thousand C) about 1023 D) None; they are blocked by the Earth's atmosphere.

A

27. If the sun's surface cooled, how would its appearance change? A) It would appear more red. B) It would appear more blue. C) It would become bright white. D) It would stay the same.

A

7. What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse? A) outward pressure due to super-heated gas B) the strong force between protons C) electromagnetic repulsion between protons D) neutrinos produced by nuclear fusion drag gas outward

A

9. By what process do nuclear power plants on the Earth generate energy? A) nuclear fission B) nuclear fusion C) chemical reactions D) converting kinetic energy into electricity E) converting gravitational potential energy into electricity

A

1. Which of the following is the phase of matter in the Sun? A) gas B) plasma C) liquid D) solid E) a mixture of all of the above

B

10. Hydrogen fusion in the Sun requires a temperature, in Kelvin, of A) thousands of degrees. B) millions of degrees. C) billions of degrees. D) trillions of degrees. E) any temperature, as long as gravity is strong enough.

B

12. How much mass does the Sun lose through nuclear fusion per second? A) 4 tons B) 4 million tons C) 600 tons D) 600 million tons E) Nothing; mass-energy is conserved.

B

22. What are coronal holes? A) regions in the photosphere where magnetic lines gather, creating cooler areas with much less plasma B) areas of the corona where magnetic field lines project out into space, allowing charged particles to escape and form the solar wind C) areas in the corona that allow us to see through to the photosphere D) tunnels in the outer layers of the Sun that allow photons to escape and form the solar wind E) all of these answers

B

5. Sunspots are cooler than the surrounding gas in the photosphere because A) they are regions where convection carries cooler material downward. B) strong magnetic fields slow convection and prevent hot plasma from entering the region. C) magnetic fields trap ionized gases that absorb light. D) there is less fusion occurring there. E) magnetic fields lift material from the sunspot and quickly cool the material.

B

6. At the time the hypothesis was suggested, what major problem was identified with the idea that the Sun was powered by gravitational contraction? A) Contracting objects cool down rather than heat up. B) This process would power the Sun for only about 25 million years, but geologists already had evidence the Earth was much older than that. C) This process could not possibly lead to the observed power output of the Sun. D) 19th century astronomers should have been able to measure the required change in the Sun's size.

B

8. By what process does the Sun generate energy? A) nuclear fission B) nuclear fusion C) chemical reactions D) gravitational contraction E) gradual expansion

B

15. What would happen to the core of the sun if its temperature rose slightly? A) The rate at which fusion occurs would decrease, leading to a contraction of the core, which would in turn cause a further temperature rise. B) The rate at turn cause the which fusion occurs would increase, leading to a contraction of the core, which would in temperature to rise even further. C) The rate at turn cause the which fusion occurs would increase, leading to an expansion of the core, which would in temperature to drop back down. D) The rate at turn cause the which fusion occurs would decrease, leading to an expansion of the core, which would in temperature to drop back down.

C

23. Why do sunspots appear dark? A) They are composed of different elements than the rest of the sun. B) They are thick clouds on the sun, blocking its light. C) They are regions that are significantly cooler than the rest of the photosphere. D) They are regions nearly devoid of gas.

C

24. Which of the following statements about the sunspot cycle is not true? A) The number of sunspots peaks approximately every 11 years. B) The magnetic polarity of the Sun reverses approximately every 11 years. C) The rate of nuclear fusion in the Sun peaks about every 11 years. D) At solar minimum, the first sunspots form at mid-latitudes on the Sun. E) The number of solar flares peaks about every 11 years.

C

3. The core of the Sun is A) at the same temperature and density as its surface. B) at the same temperature but much denser than its surface. C) much hotter and much denser than its surface. D) constantly rising to the surface through convection. E) composed of iron.

C

4. Based on its surface temperature of 6,000 K, most photons that leave the Sun's surface lie in which region of the electromagnetic spectrum? A) microwave B) infrared C) visible D) ultraviolet E) X-ray

C

13. Suppose you try to bring two protons close together. Because of the electromagnetic force, the two protons will A) collide. B) remain stationary. C) attract one another. D) repel one another. E) join together to form a deuterium nucleus.

D

17. Studies of solar vibrations have revealed that A) the Sun vibrates only on the surface. B) they are caused by processes similar to those that create earthquakes. C) the Sun generates energy by nuclear fusion. D) our mathematical models of the solar interior are fairly accurate. E) neutrinos from the solar core reach the solar surface easily.

D

18. Imagine that you are trying to stop neutrinos with a lead shield. How thick would you need to make this shield to ensure that it can stop a neutrino? A) about one meter B) about 700,000 kilometers, i.e. the radius of the Sun C) about 150 million kilometers, i.e. the size of an astronomical unit D) about one light year E) about 14 billion light years, i.e. the size of the observable universe

D

2. Which is closest to the temperature of the Sun's core? A) 10,000 K B) 100,000 K C) 1 million K D) 10 million K E) 100 million K

D

25. Which of the following processes is involved in the sunspot cycle? A) a slight gravitational contraction of the Sun B) small variations in the rate of nuclear energy generation in the solar interior C) an imbalance in the operation of the solar thermostat D) the winding of magnetic field lines due to the Sun's rotation E) a large change in the amount of visible light emitted by the Sun

D

26. What observations characterize solar maximum? A) The Sun becomes much brighter. B) The Sun emits light of longer average wavelength. C) The Sun rotates faster at its poles. D) There are many sunspots visible on the surface of the Sun. E) all of these answers

D

11. At the center of the Sun, nuclear fusion converts hydrogen into A) hydrogen compounds such as methane. B) molecular hydrogen. C) radiation and elements such as carbon and nitrogen. D) radioactive elements such as uranium and plutonium. E) helium, gamma rays, and neutrinos.

E

20. What is the solution to the solar neutrino problem? A) The Sun is generating energy other than by nuclear fusion. B) The Sun is generating much less energy than we think it is. C) We did not know how to detect neutrinos. D) Not all fusion reactions create neutrinos. E) The electron neutrinos created in the Sun's core change into another type of neutrino that we did not detect.

E

21. The light radiated from the Sun's surface reaches Earth in about 8 minutes. However, the energy of this light was released by fusion in the Sun's core about A) 8 minutes ago. B) 11 years ago. C) several hundred years ago. D) several thousand years ago. E) several hundred thousand years ago.

E