Question 1

State the two laws of thermal radiation.

Accepted Answer

The answer of State the two laws of thermal radiation....

Question 2

Briefly explain why spectral lines are useful in determining the chemical composition of their source.

Accepted Answer

The answer of Briefly explain why spectral lines are useful...

Question 3

Atomic number refers to ________.

Accepted Answer

The answer of Atomic number refers to ________....

Question 4

The most common isotope of gold has atomic number 79 and atomic mass number 197. How many protons and neutrons does the gold nucleus contain? Assuming the gold is electrically neutral, how many electrons does it have?

Accepted Answer

The answer of The most common isotope of gold has...

Question 5

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

Accepted Answer

The fact that the hydrogen spectral line appears at a longer wavelength in the star's spectrum means that the star is moving away from us. This is because of the Doppler effect - the wavelength of light emitted by an object moving away from us is shifted towards the red end of the spectrum (i.e. a longer wavelength).

Question 6

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

Accepted Answer

X-rays and radio waves both travel at the same speed in a vacuum, which is the speed of light. Therefore, statement A is not true.

Question 7

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 8

Imagine that the sun ceased emitting light at wavelengths from about 600 to 700 nm. How would this look to us, and why?

Accepted Answer

The answer of Imagine that the sun ceased emitting light...

Question 9

The most common isotope of oxygen has atomic number 8 and atomic mass number 16. Another isotope has two extra neutrons. What are the atomic number and atomic mass number of this isotope?

Accepted Answer

The answer of The most common isotope of oxygen has...

Question 10

Briefly explain how we can use spectral lines to determine an object's radial motion (toward or away from us). Can we also learn the object's tangential motion (across our line of sight)from its spectral lines?

Accepted Answer

The answer of Briefly explain how we can use spectral...

Question 11

Explain how adaptive optics works.

Accepted Answer

The answer of Explain how adaptive optics works....

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...

Question 13

White light hitting white paper is an example of

Accepted Answer

White light hitting white paper primarily results in reflection or scattering, which is why we see the paper as white. The paper reflects most of the visible light spectrum, rather than absorbing or emitting it.

Question 14

The resolution of a 10- meter telescope is about 0.01 arcsecond for visible light. Would you expect the angular resolution of a 10- meter radio telescope 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...

Question 15

Suppose the surface temperature of the Sun were about 18,000 K, rather than 6,000 K. How would the thermal radiation spectrum of the Sun be different?

Accepted Answer

The answer of Suppose the surface temperature of the Sun...

Question 16

Explain what an interferometer is and give an example.

Accepted Answer

The answer of Explain what an interferometer is and give...

Question 17

Imagine that the sun began glowing half as bright at all visible wavelengths, but glowed much brighter in the infrared. How would this look to us, and why?

Accepted Answer

The answer of Imagine that the sun began glowing half...

Question 18

Suppose an astronomer proposed to build a major observatory on the campus of your school. Would it make a good observing site? Explain why or why not.

Accepted Answer

The answer of Suppose an astronomer proposed to build a...

Question 19

An isotope of fluorine has 9 protons and 10 neutrons. What are the atomic number and atomic mass number of this fluorine? If we added a proton to this fluorine nucleus, would the result still be fluorine? What if we added a neutron instead? Explain.

Accepted Answer

The answer of An isotope of fluorine has 9 protons...

Question 20

Define atomic mass number.

Accepted Answer

The answer of Define atomic mass number....

Quiz 5: Light: the Cosmic Messenger