stars and galaxies test 2

The time taken for neutrinos generated in the thermonuclear reactions at the center of the Sun to escape from its surface is

a few seconds

What is a plasma?

a gas-like mixture of ions and electrons

What is a spicule on the Sun?

a jet of rising gas in the chromosphere

A typical refracting telescope is made up of

a long-focal-length lens at the front and a short-focal-length lens at the rear (next to your eye as you look through the telescope).

At the present time, the energy of the Sun is generated

in its central core only, by fusion of hydrogen nuclei.

Where is most of the mass of the Sun concentrated?

in the inner core

If the temperature of the surface of the Sun doubled, the amount of energy we would receive would

increase by a factor of 16.

If the Sun were the same temperature but twice its present diameter, the amount of energy we would receive would

increase by a factor of four

Over what range of wavelengths does the Hubble Space Telescope operate?

infrared, visible, and ultraviolet

A radio telescope

is very similar to a reflecting optical telescope.

The radius of the Sun is about 1/200 of an AU. What happens to the flux of solar energy as it travels from the Sun's surface to Earth?

it decreases by a factor of (200)2 = 40,000.

The temperature at the top of the clouds on Jupiter is about 165 K. In degrees Celsius, this is

-108°C.

If all effects caused by Earth's atmospheric variations (seeing) could be removed from the visible image of a star on one of the 10-m diameter Keck telescopes on Hawaii, what would be the angular resolution achievable by this telescope in arcseconds for light of wavelength 500 nm? (1 nm = 10-9 m)

0.00125 arcsec

The shortest wavelength observed by HST is 115 nm with objective mirror 2.4m. What is its angular resolution at this wavelength?

0.01 arcsec

Material in solar spicules is ejected out of the Sun at typical speeds of 20 km/s. What would be the observed wavelength of the Balmer H hydrogen spectral line emitted by this gas, compared to that from stationary solar material? (See Box 5-6 of Universe, 10th ed.)

0.044 nm shorter than the H from stationary solar materi

When four protons collide to form helium, what fraction of the original mass of the protons is converted to energy?

0.7%

An electron is in the n = 3 energy level in a hydrogen atom. To ionize this atom it is necessary for the electron to gain a minimum of how much energy?

1.5 eV

Hydrogen gas emits a strong spectral line of red light with a wavelength of 656.3 nm (Balmer line). This emission line is seen in the spectrum of a distant quasar but at a wavelength of 721.9 nm. Applying Doppler's relation, how fast is this object moving with respect to Earth, in terms of the velocity of light, c?

1/10 c

The core of the Sun, in which all the Sun's thermonuclear energy is produced, takes up about

1/4 of the Sun's radius.

A particular photon of ultraviolet (UV) light has a wavelength of 200 nm and a photon of infrared (IR) light has a wavelength of 2000 nm. What is the energy of the UV photon compared to the IR photon?

10 times more energy than the IR photon

The average distance of Pluto from the Sun is 40 AU. How long does it take for light to travel across the solar system from one side of Pluto's orbit to the other?

11 hrs

The fissionable isotope of uranium used in nuclear weapons, 235U, whose atomic number is 92, has what total number of protons and neutrons in its nucleus?

143

How far apart from each other would Galileo and his assistant had to have been in order for the round trip time for their beam of light to have been one second?

150,000 km

A piece of iron is heated from 400 to 800 K (127 to 527°C). By what factor will the total energy per second emitted by this iron increase?

16

What is the magnification of a Newtonian telescope with a primary mirror of diameter 0.25 m and focal length of 4 m when used with an eyepiece of focal length 25 mm and an optical diameter of 2.5 mm?

160

A refracting telescope has an objective lens of focal length 80 cm, a diameter of 10 cm, and an eyepiece of focal length 5 cm and diameter 1 cm. What is the magnifying power of this telescope?

16×

The average time taken for energy generated by thermonuclear fusion in the center of the Sun to reach the surface layers and escape is calculated to be

170,000 years

What type of radiation is emitted by hot hydrogen gas when electrons jump from the n = 8 level to the n = 7 level of the atoms?

19.05 m, in the infrared

An astronomer observing the spectrum of the Sun finds that the Balmer Hß spectral line ( = 486 nm) on the solar equator at one edge of the Sun's disk is blueshifted by 0.0033 nm compared to the same line at the center of the Sun's disk and is redshifted by the same amount on the equator at the other side of the Sun's disk. If this Doppler shift is due to the Sun rotating (try drawing a diagram), then the rotational speed of the Sun at its equator is

2 km/s.

The human eye is most sensitive to light with a wavelength near 550 nm. To what photon energy is the human eye most sensitive?

2.25 eV

The proton, the nucleus of the hydrogen atom, has a mass that exceeds that of the electron by approximately what factor?

2000

A particular reflecting telescope has an objective mirror with a focal length of 1.2 m and an eyepiece lens of focal length 6 mm. What is the magnifying power of this telescope?

200×

At the present time, overall solar magnetic activity, including sunspots, seems to vary almost periodically with a timescale of

22 years.

What is the wavelength of radio waves from the FM radio station KTYD, which operates at the frequency 99.9 MHz?

3.0 m

A typical but very cool star might have a temperature of 3100°C. On the Kelvin scale, this is about

3373 K

How many times more light can the 10-m diameter Keck telescope on Mauna Kea in Hawaii collect than an average unaided human eye that has a typical aperture diameter of 5 mm?

4 × 10^6

A refracting telescope has an objective lens of focal length 80 cm, a diameter of 10 cm, and an eyepiece of focal length 5 cm and diameter 1 cm. How much more light will this telescope collect than the average unaided eye whose focal length is 2 cm and diameter is 0.5 cm?

400

If the wavelengths of H and Hß, the first two lines of the hydrogen Balmer series, are 656.3 nm and 486.2 nm, respectively, what is the wavelength of H, the third line of the Balmer series?

434.1 nm

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 max T = 2.9 × 106 , with T in kelvins and in nanometers (nm), what is the expected peak wavelength of the continuum spectrum of the Sun?

500 nm

If the temperature near the center of a particular sunspot is 4350 K and the temperature of the surrounding photosphere is 5800 K, then the energy flux (energy passing through each square meter per second) from the center of the sunspot is what fraction of the energy flux from the surrounding photosphere?

56%

The human eye has evolved over time so that its peak wavelength sensitivity is about 0.5 m (1 m = 10-6 m). Use Wien's law to calculate the temperature of blackbody radiation to which the eye is most sensitive.

5800 K

How much matter is converted into energy in the Sun each second?

6.0 × 1011 kg

The photosphere is the level of the Sun from which most of the visible radiation we see originates. The temperature of the base of the Sun's photosphere is roughly

6000 K

A department store sells an "astronomical telescope" with an objective lens of 30 cm focal length and an eyepiece lens of focal length 5 mm. What is the magnifying power of this telescope?

60×

How fast and in what direction is a star moving if its spectrum contains a line that shifts from 486.2 nm to 486.3 nm?

61.7 km/s away from you

The isotope 15N has an atomic number of 7. This isotope

7 protons and 8 neutrons

The total energy emitted per unit time at all wavelengths from an object increases by what factor if its temperature is increased by a factor of 3 (e.g., from room temperature to 900 K)?

81

You are asked to design a detection system for human beings (or animals) in darkness, using infrared detection. If human beings are at a temperature of about 310 K, what would need to be the wavelength of peak sensitivity of your equipment or cameras (1 m = 10-6 m)? (Hint: Use Wien's law.)

9.35 m

How is a star's spectrum changed when looking at the absorption spectrum from a star moving away from you as compared to if the star were stationary?

All the absorption lines would shift toward the long wavelength end of the spectrum, each line shifting by an amount proportional to its wavelength

How does angular resolution for a given diameter of telescope depend on wavelength?

Angular resolution worsens as wavelength increases

The star Betelgeuse has a lower surface temperature than the Sun; therefore (with IR = infrared and UV = ultraviolet)

Betelgeuse emits less IR and less UV flux than the Sun.

Which of the following does not experience differential rotation?

Earth

Why is the solar corona so much hotter than the photosphere?

Energy is carried upward through the chromosphere by magnetic fields

The laws governing the energy flux F and wavelength of maximum intensity max of emitted radiation from a hot, dense body whose temperature is T are given by (where and a are constants)

F = T^4, max T = a.

What stops the Sun from collapsing under the force of its own gravity?

It is held up by the pressure of the very high temperature gas within it.

A small particle of interplanetary material is heated by friction from 400 K to 4000 K as it falls into the atmosphere of Earth and produces a meteor or a shooting star in our sky. If this object behaves like a perfect blackbody over this short time, how does its emitted radiation change as it is heated?

Its emitted intensity rises by a factor of 10,000, while its peak wavelength becomes shorter by a factor of 10, from infrared to red visible light

Balmer constructed his formula for the hydrogen spectral lines by trial and error manipulations of large amounts of experimental measurement data. This is somewhat

Kepler in discovering his laws of planetary motion

You begin with an object at a certain temperature, and you increase its temperature by an amount T. For which one of the following values of T will the final temperature of the object be lowest?

T = 10° Fahrenheit

Why is the sky blue?

The air molecules scatter blue light better than red light, so more blue light reaches our eyes.

The granulation that is observed on the photosphere of the Sun appears to be the result of

convection currents.

What happens when a beam of white light (containing all colors) is passed through a prism of glass

The speed of the red light that leaves the prism is higher than that of the blue light, leading to a colored beam.

What happens to the positrons produced by the nuclear reactions in the core of the Sun?

They collide with electrons, producing energy

Choose the correct sequence of electromagnetic radiations, in order of increasing wavelengths.

UV, visible, IR, radio

Which one of the following statements is true?

Visible light takes up only a very small part of the total range of wavelengths in the electromagnetic spectrum.

What is the Zeeman effect?

When a light source is located in a magnetic field, the spectral lines it emits are split into two or more components

Suppose an astronomical satellite observes the Crab Nebula at a wavelength of 0.85 nm. In what wavelength range is this satellite observing?

X rays

High energy telescopes detect the radiation at the high-energy end of the electromagnetic spectrum, namely

X rays and gamma rays.

The extremely high gas temperatures in the solar corona mean that this region is best observed at wavelengths of

X rays.

Can a cooler object ever emit more radiation than a warmer object?

Yes, if the cooler object has an area Acooler that meets the requirement (Tcooler )4Acooler > (Thot )4 Aho

Sunspots are

cooler, darker regions on the Sun's surface.

What is a positron?

a positive electron

An electromagnetic wave has a wavelength of 80 cm. This wave is

a radio wave.

The neutrino is

a tiny particle that interacts very weakly with matter, with extremely low or zero mass and no charge

The energy flux arriving at Earth from the Sun is known as the solar constant and has a value of 1.37 × 103 watts per square meter. Assuming that the atmosphere absorbs 50% of the energy and that a 5-m2 roof collector is available to collect energy with a 30% efficiency, how much of this solar energy would then be available for use in the house for water or house heating, etc.? (1 KW = 1 kilowatt = 1000 W)

about 1 KW

What is the rotation period of the Sun?

about one rotation per month

An ideal blackbody in physics and astronomy is an object that

absorbs and emits electromagnetic radiation at all wavelengths.

Chromatic aberration occurs in a refracting telescope when

all colors of light do not come to the same focal point.

The light-gathering power of a telescope is related directly to the

area of its primary mirror or lens.

in its interaction with matter, light behaves

as both waves and particles, depending on the type of interaction

Radio waves travel through space at what speed?

at the speed of light, 3 × 108 m/s

The energy flux F from a star is the

average amount of energy emitted by each square meter of the star's surface each second.

The temperature of a gas cloud in space is directly related to and representative of the

average speed of its atoms.

When a ray of light strikes a smooth mirror surface at an angle to the perpendicular, the ray is reflected

back along its original (incoming) path.

The phrase "'hydrostatic equilibrium"' in the Sun refers to the

balance of gravity inward and gas pressure outward.

The resolution in a telescope is best for which segment of the visible spectrum?

blue

A photon is a(n)

bundle of pure energy.

Electrons in atoms

can have any energy

The energy transfer process that operates in the Sun via mass motion is known as

convection

A spherical mirror suffers from spherical aberration because

different parts of the mirror focus the light at different distances from the mirror.

How can we characterize the rotation of the Sun?

differential rotation, with the equator rotating faster than the poles

Spectral lines are of particular importance in astronomy because

each different element has a characteristic line spectrum

An electron volt (eV) is a unit of

energy.

The Balmer series of spectral lines at visible wavelengths are emitted by a hot hydrogen gas when the electrons fall from all higher atomic energy levels to the

first excited level, n = 2

What is the source of the solar wind?

gas escaping through coronal holes

The main reason for placing astronomical telescopes and detectors on satellites is to

get above the absorption in Earth's atmosphere.

Violet light differs from red light in that violet light

has a shorter wavelength than red light.

Which of the following physical products is not produced by the Sun during the thermonuclear process, in which hydrogen nuclei are combined together in its core

heavy nuclei such as uranium

The corona contains very little energy because

its temperature is high but there are very few atoms

The major feature that distinguishes a sunspot from other regions on the Sun is

its very powerful magnetic field.

Thermonuclear fusion reactions in the core of the Sun convert four hydrogen nuclei into one helium nucleus. The helium nucleus has

less mass than the four hydrogen nuclei, the lost mass becoming energy in an amount given by E = mc2

Compared to its speed in a vacuum (or in space), the speed of light in glass is

less.

One way to improve the angular resolution of a radio telescope is to

make the dish size larger.

The Sun emits light

most intensely in the visible.

Compare two electron transitions in hydrogen: n = 3 n = 1 and n = 2 n = 1. Which produces the photon with the higher frequency?

n = 3 n = 1

The basic makeup of an atom is

negative and positive charges mixed uniformly over the volume of the atom

An example of an object that emits no radiation at all is a(n)

object at a temperature of 0 K.

If all stars are considered to be perfect blackbodies, then it should follow that all stars

of the same temperature emit the same energy flux

A Newtonian telescope consists of which of the following combinations of optical elements?

one concave and one flat mirror

Solar flares occur at what positions on the solar disk?

only within sunspot groups

What name is given to the visible "surface" of the Sun?

photosphere

In order from lowest to highest, what are the names of the three layers in the Sun's atmosphere?

photosphere, chromosphere, corona

An ionized hydrogen atom is simply a(n)

proton

The two most important processes by which energy is transported from the core of the Sun to the photosphere are

radiation and convection.

One major difference between radio waves and light is that

radio waves have lower frequencies.

The photosphere is

rather opaque to visible light because negative hydrogen ions absorb light

In order of increasing frequency, some of the colors that the visible spectrum contains are

red, yellow, and blue.

Solar sound waves

reflect back and forth between the solar surface and layers deep in the solar interior

Isotopes of a particular element in the periodic table have which nuclear property in common

same number of protons but different numbers of neutrons

When white light passes through a prism or a lens, which wavelengths of light are deflected most by the glass?

shorter wavelengths

Atoms in a thin, hot gas (such as a neon advertising sign) emit light at

specific wavelengths, depending on the element.

The chemical makeup of a star's surface is obtained by

spectroscopy of the light emitted by the star

The chemical composition of the surface layers of the Sun is determined primarily by

spectroscopy.

In what way does a photon of blue light not differ from a photon of yellow light in a vacuum?

speed

What is the refraction of light?

the change in direction of a light ray as it crosses from a less dense, transparent material to a more dense one

What is the name of the layer of the Sun's atmosphere that appears as a pinkish ring just outside the visible disk of the Sun during a total solar eclipse?

the chromosphere

Which part of the Sun has the lowest density?

the corona

What is magnetic reconnection?

the rearrangement of magnetic fields in adjacent arches in the solar atmosphere, with the consequent release of great energy

A light ray strikes a smooth surface of glass at an angle to the perpendicular. What angle will the reflected ray make with the perpendicular to the surface?

the same angle on the opposite side of the perpendicular to the incident ray

What is the corona on the Sun?

the sun's outer atmosphere

What is the main reason for combining many radio telescopes together into an interferometer with large distances between telescopes?

to obtain much sharper images of sources

An astronomer photographs the spectrum of an object and finds a spectral line at 499 nm wavelength. In the laboratory, this spectral line occurs at 500 nm. According to the Doppler effect, this object is moving

toward Earth at 1/500 the speed of ligh

What is nuclear fusion?

two nuclei sticking together to form a new, heavier nucleus

The two ranges of electromagnetic radiation for which Earth's atmosphere is reasonably transparent are

visible and radio radiation

The dark lines in the solar spectrum are caused by

wavelengths that have been absorbed by atoms between us and the source of the light.

The contraction of a star (or other object) due to its own gravity generates heat. If this process, known as the Kelvin-Helmholtz contraction, were to be the source of heat energy from the Sun, then the Sun's age

would be about 25 million years