5 Written questions
5 Matching questions
- 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?
A) The star is moving toward us.
B) The star is moving away from us. C) The star is getting hotter.
D) The star is getting colder.
E) The "star" actually is a planet.
- Which of the following statements about thermal radiation is always true?
A) A hot object emits more radiation per unit surface area than a cool object.
B) A cold object produces more total infrared and radio emission per unit surface area than a hot object.
C) A hot object produces more total infrared emission than a cooler object.
D) All the light emitted by hot object has higher energy than the light emitted by a cooler object.
- An isotope of fluorine has 9 protons and 10 neutrons. What are the atomic number and atomic weight 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.
- When white light passes through a cool cloud of gas, we see
A) visible light.
B) infrared light.
C) thermal radiation.
D) an absorption line spectrum.
E) an emission line spectrum.
- The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?
A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
B) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the blue light that is present in the Sun's spectrum.
C) Neptune's spectrum would peak at a much longer wavelength than the Sun's spectrum.
D) There is no way to predict the answer to this question, since planets and stars are made of such different things.
- a A) A hot object emits more radiation per unit surface area than a cool object.
- b D) an absorption line spectrum.
- c The atomic number of fluorine is equal to the number of protons, 9. The atomic weight is equal to the number of protons plus neutrons, 19. If we added a proton, it would no longer be fluorine. If we added a neutron instead, it would just be another isotope of fluorine, with atomic number 9 but atomic weight 20.
- d B) The star is moving away from us.
- e A) The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
5 Multiple choice questions
- A) Electrons orbit the nucleus rather like planets orbiting the Sun.
- C) An electron moves from an upper energy level to a lower one.
- A) The temperature of the corona's gas is some 1 to 2 million Kelvin.
- 1. Hotter objects emit more radiation per unit surface area.
2. Hotter objects emit photons with higher average energy.
5 True/False questions
The energy levels of an element and its ion are the same. → False
The spectra of most galaxies show redshifts. This means that their spectral lines ________.
A) have wavelengths that are longer than normal
B) always are in the red part of the visible spectrum
C) have wavelengths that are shorter than normal
D) have a higher intensity in the red part of the spectrum → A) have wavelengths that are longer than normal
No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?
A) a hot, thin (low-density, nearly transparent) gas
B) a filament in a standard (incandescent) light bulb
C) a star
D) you → D) a thermal emitter.
The frequency of a wave is
A) the number of peaks passing by any point each second.
B) measured in cycles per second.
C) measured in hertz (Hz).
D) equal to the speed of the wave divided by the wavelength of the wave.
E) all of the above → E) all of the above
Without telescopes or other aid, we can look up and see the Moon in the night sky because it
A) emits visible light.
B) emits thermal radiation.
C) reflects infrared light.
D) reflects visible light.
E) glows through radioactive decay. → False