AST 1002 Homework 9 – Flashcards

When a rod of metal is heated intensely, its predominant color will A) remain red as the intensity of light increases. B) change from red through orange to white and then to blue. C) change from blue through white, then orange, and finally red, when it becomes red-hot at its hottest. D) be white, all colors mixed together, as the intensity of light increases.

An ideal blackbody in physics and astronomy is an object that A) emits only infrared light and hence appears black to the eye. B) does not emit or absorb any electromagnetic radiation. C) absorbs and emits electromagnetic radiation at all wavelengths. D) absorbs all electromagnetic radiation but emits none.

You observe two stars of the same surface temperature, but one has twice the diameter of the other. How many times larger is the energy flux from the larger star compared with that from the smaller star? A) 2 B) 4 C) 16 D) They are the same.

Stars A and B have the same radius, but the spectrum of star A peaks at a wavelength of 500 nm, whereas star B's spectrum peaks at 1000 nm. What is the ratio of the Kelvin temperature of the surface of star A to the Kelvin temperature of the surface of star B? A) 1/4 B) 1/2 C) 2 D) 4

The dark absorption lines in the solar spectrum are caused by A) a cooler layer of gas overlying the hot solar surface, which contains many elements, including hydrogen, helium, magnesium, calcium, and iron. B) a cooler layer overlying the hot solar surface, consisting solely of hydrogen gas, which produces all the absorption lines. C) absorption by atoms and molecules in Earth's cool atmosphere. D) a hotter layer of gas that overlies the cooler solar surface and produces the absorption lines.

An astronomer finds a source of light in space that emits light only in specific, narrow emission lines. Kirchhoff's laws lead him to which conclusion? A) The source cannot consist of gases but must be a solid object. B) The source is made up of a hot, dense gas. C) The source is made up of a hot, low-density gas. D) The source is made up of a hot, dense gas surrounded by a rarefied gas.

The specific colors of light emitted by an atom in a hot, thin gas (e.g., in a neon tube, a fluorescent bulb, or a gas cloud in space) are caused by A) an electron dropping into the nucleus, producing small nuclear changes. B) electrons jumping to lower energy levels, losing energy as they do so. C) protons jumping from level to level. D) vibrations of the electrons within the atom.

What term is given to the visible "surface" of the Sun? A) prominence B) corona C) chromosphere D) photosphere

The temperature of the Sun's photosphere is A) close to 1 million K. B) about 10,000 K. C) 5800 K. D) 4300 K.

If the temperature of the solar surface is 5800 K and Wien's law for the peak wavelength of the spectrum of the Sun, assumed to be a blackbody, is given by λmax T = 2.9 × 106, with T in Kelvins and λ in nanometers (nm), what is the expected dominant wavelength of the Sun? A) 600 nm B) 500 nm C) 300 nm D) 50 nm

The visible light coming from the solar chromosphere is dominated by light of what color? A) indigo B) blue C) green D) red

Spicules on the solar surface are A) jets of gas surging out of the photosphere of the Sun into the chromosphere, usually at supergranule boundaries. B) intense eruptions from sunspot groups and active regions, associated with solar flares. C) streams of solar coronal material, usually seen only during a total solar eclipse. D) curtainlike structures hanging over sunspot regions.

Which part of the Sun is the least dense? A) corona B) chromosphere C) photosphere D) core

The highest temperatures in the Sun are found in the A) solar interior. B) photosphere. C) chromosphere. D) corona.

The temperature of the corona of the Sun is A) about the same as that of the photosphere, 5800 K. B) very cool because it is the farthest part of the Sun from the heat source. C) about twice as hot as the photosphere, 12,000 K. D) very hot, about 106 K.

Which one of the following is not considered to be a feature of the quiet Sun? A) solar wind B) sunspot C) spicule D) granule

A typical sunspot group lasts A) virtually forever. B) about two months. C) 11 years. D) 22 years.

What is the average length of time from one maximum in the number of sunspots on the Sun to the next maximum? A) 22 years B) 7 years C) 11 years D) 4.5 years

Sunspots appear dark because they A) are coronal holes. B) are cooler than the surrounding surface. C) are regions from which the light is prevented from escaping by strong magnetic fields. D) have a different chemical composition than the surrounding surface.

What is the energy source for the Sun? A) thermonuclear fusion in the core B) radioactive decay of the nuclei of heavy elements C) primordial heat, left behind from when the Sun first formed D) heat released by gravitational contraction as the Sun slowly shrinks