Astronomy Chapter 3 Key Terms

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Electromagnetic Radiation
Another term for light, electromagnetic radiation transfers energy and information form one place to another.
Visible Light
The small range of the electromagnetic spectrum that human eyes perceive as light. The visible spectrum ranges fro about 400-700 nm, corresponding to blue through red light.
Radio Waves
Electromagnetic radiation with wavelength in the radio part of the spectrum.
Infrared Waves
Region of the electromagnetic spectrum just outside the visible range, corresponding to light of a slightly longer wavelength than red light. Electromagnetic radiation with wavelength in the infrared part of the spectrum.
Ultraviolet Waves
Region of the electromagnetic spectrum, just beyond the visible range, corresponding to wavelengths slightly shorter than blue light.
X Rays
Region of the electromagnetic spectrum corresponding to radiation of high frequency and short wavelength, far beyond the visible spectrum.
Gamma Rays
Region of the electromagnetic spectrum, far beyond the visible spectrum, corresponding to radiation of very high frequency and very short wavelength.
A pattern that repeats itself cyclically in both time and space. Waves are characterized by the speed at which they move, their frequency, and their wavelength.
The time needed for an orbiting body to complete one revolution around another body.
The distance from one wave crest to the next, at a given instant in time.
The maximum deviation of a wave above or below zero point.
The number of wave crests passing any given point in a unit time.
An elementary particle with a negative electric charge one of the components of the atom.
An elementary particle carrying a positive charge, a component of all atomic nuclei. The number of protons in the nucleus of an atom dictates what type of atom it is.
Electric Field
A field extending outward in all directions from a charged particle, such as a proton/electron. The electric field determines the electric force exerted by the particle on all other charged particles in the universe; the strength of the electric field decreases with increasing distance from the charge according to an inverse-square law.
Magnetic Field
Field that accompanies any changing electric field and governs the influence of magnetized objects on one another.
The union of electricity and magnetism, which do not exist as independent quantities but are in reality two aspects of a single physical phenomenon.
Speed of Light
The fastest possible speed, according to the currently known laws of physics. Electromagnetic radiation exists in the form of waves/photons moving at the speed of light.
Wave Theory of Radiation
Description of light as a continuous wave phenomenon, rather than as a stream of individual particles.
Electromagnetic Spectrum
The complete range of electromagnetic radiation, from radio to gamma rays, including the visible spectrum. All types of electromagnetic radiation are basically the same phenomenon, differing only by wavelength, and all move at the speed of light.
A quantity that measures a material’s ability to block light. Opposite of transparency.
A measure of the amount of heat in an object, and an indication of the speed of the particles that compromise it.
Blackbody Curve
The characteristic way in which the intensity of radiation emitted by a hot object depends on frequency. The frequency at which the emitted intensity is highest is an indication of the temperature of the radiating object. Planck Curve.
Wien’s Law
Relation between the wavelength at which a blackbody curve peaks and the temperature of the emitter. The peak wavelength is inversely proportional to the temperature, so the hotter the object, the bluer its radiation.
Stefan’s Law
Relation that gives the total energy emitted per square centimetre of its surface per second by an object of a given temperature. Shows that energy emitted increases rapidly with an increase in temperature, proportional to the temperature raised to the fourth power.
Doppler effect
Any motion-induced change in the observed wavelength (or frequency) of a wave.
Categories: Astronomy