Chapter 5 Flashcards
Radiative Energy:
Energy that light carries
Power:
The rate of energy flow, measured in watts
emmission:
a light bulb emits visible light, the energy of the light comes from the electrical potential energy supplied to the light bulb
Absorption:
When you place your hand near an incandescent light bulb the hand absorbs some of the light and warms the hand
Transmission:
some forms of matter transmit light, or allows light to pass through it
Reflection/scattering:
light can bounce off matter leading it to reflect, when light is bouncing all in the same direction, or scatter, when light is bouncing in all different directions
Particles:
atoms and molecules that make up physical objects
Waves:
carry energy outward, but do not carry the particles themselves
What are the three basic properties of waves:
wavelength, frequency, and speed
Wavelength:
the distance from one peak to the next
Frequency:
The number of peaks passing by any point in a second
Speed:
how fast the waves travel, equal to wavelength x frequency
Photon
particle of light
Molecules
combinations of atoms
Compound
molecule with two or more types of atoms
Chemical bond
describes interactions between electrons that bind atoms together
Pressure
the force per unit pushing on an object’s surface, high pressure can cause gas to dissolve into a liquid, or reverse the stages of matter
Continuous Spectrum
the spectrum of an dense object (such as a lightbulb) that spans all visible wavelengths without interruption
Emission Line Spectrum
A low-density object (such as a gas) that emits light only at specific wavelengths that depend on its composition and temperature, producing a spectrum with bright emission lines
Absorption Line Spectrum
A combination of emission and continuous spectra.
A cloud of gas between us and a light bulb that can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum.
What property does the thermal radiation spectrum depend on
temperature
We know how fast a distant galaxy is moving away from us on the basis of its…
spectrum
According to the laws of thermal radiation, hotter objects emit photons with
a shorter average wavelength
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
its wavelength and energy
We can see the Moon because it
reflects visible light
You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?
the galaxy is moving away from you
Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
the cloud is cool and lies between you and a hot star
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma, x rays, ultraviolet, visible, infrared, micro, radio
Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
the wavelengths of spectral lines in the star’s spectrum
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star’s spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
the star is moving toward us
Thermal radiationis defined as
radiation with a spectrum whose shape depends only on the temperature of the emitting object
Suppose that Star X and Star Y both have redshifts, but Star X has alargerredshift than Star Y. What can you conclude?
Star x is moving away from us faster than star Y
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 inferfrom its red color?
the surface is cooler than the surface of the sun
Which of the following stars is the hottest?
a blue star
Which of the following observational techniques is most appropriate for measuring Doppler shifts?
spectroscopy
Suppose that two stars are identical in every way; for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth,exceptthat one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?
the faster rotating star has wider spectral lines than the slower rotating star
When an atom’s electrons fall down to lower energy levels in a thin cloud of hot gas, what is produced?
an emission line spectrum
We know the Sun is primarily made from hydrogen and helium on the basis of its
spectrum
