5 Written questions
5 Matching questions
- Gamma rays have a very small ________.
- We can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one?
A) The peak of the star's thermal emission tells us its temperature: Hotter stars peak at shorter (bluer) wavelengths.
B) The total amount of light in the spectrum tells us the star's radius.
C) We can identify chemical elements present in the star by recognizing patterns of spectral lines that correspond to particular chemicals.
D) We can look at Doppler shifts of spectral lines to determine the star's speed toward or away from us.
- Energy and power are different words for the same thing.
- When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called ________.
C) gamma rays
- Suppose the surface temperature of the Sun were about 18,000 K, rather than 6,000 K. How much more thermal radiation would the Sun emit? How would the thermal radiation spectrum of the Sun be different?
- a From the first rule of thermal radiation, we know that tripling the temperature of an object increases the amount of thermal radiation it emits per unit area by a factor of 34 = 81. Thus, increasing the surface temperature of the Sun from 6,000 K to 18,000 K would increase its thermal radiation by a factor of 81. The higher temperature of the Sun would shift the peak of its thermal radiation spectrum from its current place in the visible light region into the ultraviolet. The hotter Sun would emit more energy at all wavelengths, with the greatest output coming in the ultraviolet.
- b False
- c A) photons
- d B) The total amount of light in the spectrum tells us the star's radius.
- e D) wavelength
5 Multiple choice questions
- A) a diffraction grating
- A) gamma rays, X rays, ultraviolet, visible light, infrared, radio
- B) mostly X rays.
5 True/False questions
Emission lines from different ionization states of the same element appear in the same place in the spectrum → False
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
A) infrared, visible light, ultraviolet, X rays, gamma rays, radio
B) radio, infrared, visible light, ultraviolet, X rays, gamma rays
C) visible light, infrared, X rays, ultraviolet, gamma rays, radio
D) gamma rays, X rays, ultraviolet, visible light, infrared, radio
E) gamma rays, X rays, visible light, ultraviolet, infrared, radio → B) radio, infrared, visible light, ultraviolet, X rays, gamma rays
Thermal radiation is defined as
A) radiation produced by a hot object.
B) radiation in the infrared part of the spectrum.
C) radiation that depends only on the emitting object's temperature.
D) radiation in the form of emission lines from an object.
E) radiation that is felt as heat. → C) quantum mechanics.
Briefly explain how we can use spectral lines to determine an object's radial motion. Can we also learn the object's tangential motion (across our line of sight) from its spectral lines? → The electrons can have only specific energies and not amounts of energy in between.
Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
A) It is much brighter than the Sun.
B) Its surface is cooler than the surface of the Sun.
C) It is much more massive than the Sun.
D) It is moving away from us. → B) Its surface is cooler than the surface of the Sun.