chapter 5 Flashcards
How do we experience light?
Light carries radiative energy that it can exchange with matter. Power is the rate of energy transfer, measured in watts:1 watt = 1 joule. The colors of light contain a great deal of information about the matter with which it has interacted.
How do light and matter interact?
Matter can emit, absorb, transmit, or reflect (or scatter) light.
What is light?
Light is an electromagnetic wave, but it also comes in individual “pieces” called photons. Each photon has a precise wavelength, frequency, and energy: The shorter the wavelength, the higher the frequency and energy.
What is the electromagnetic spectrum?
In order of decreasing wavelength (increasing frequency and energy), the forms of light are radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gammarays.
What is the structure of matter?
Ordinary matter is made of atoms, which are made of protons, neutrons, and electrons. Atoms of different chemical elements have different numbers of protons. Isotopes of a particular chemical element all have the same number of protons but different numbers of neutrons. Molecules are made from two or more atoms.
What are the phases of matter?
The appearance of matter depends on its phase: solid, liquid, or gas. Some gas always vaporizes from the solid or liquid phases; solids sublimate into gas and liquids evaporate into gas. At very high temperatures, molecular dissociation breaks up molecules and ionization strips electrons from atoms; an ionized gas is called a plasma.
How is energy stored in atoms?
Electrons can exist at particular energy levels within an atom. Energy level transitions, in which an electron moves from one energy level to another, can occur only when the electron gains or loses just the right amount of energy.
What are the three basic types of spectra?
There are three basic types of spectra: a continuous spectrum, which looks like a rainbow of light; an absorption line spectrum, in which specific colors are missing from the rainbow; and an emission line spectrum, in which we see light only with specific colors against a black background.
How does light tell us what things are made of?
Emission lines or absorption lines occur only at specific wavelengths that correspond to particular energy level transitions in atoms or molecules. Every kind of atom, ion, and molecule produces a unique set of spectral lines, so we can determine composition by identifying these lines.
How does light tell us the temperatures of planets and stars?
Objects such as planets and stars produce thermal radiation spectra, the most common type of continuous spectra. We can determine temperature from these spectra because hotter objects emit more total radiation per unit area and emit photons with a higher average energy.
How does light tell us the speed of a distant object?
The Doppler effect tells us how fast an object is moving toward or away from us. Spectral lines are shifted to shorter wavelengths (a blueshift) in objects moving toward us and to longer wavelengths (a redshift) in objects moving away from us.
