Electromagnetic Spectrum Flashcards
Objects also _____ that has been emitted by other objects.
Reflect radiation
All objects emit __? Except objects at __?
Electromagnetic Radiation, Absolute Zero
The most familiar form of Electromagnetic Radiation
Visible Light
Generated by several mechanisms, including changes in the energy levels of electrons, acceleration of electrical charges, decay of radioactive substances, and the thermal motion of atoms and molecules
Electromagnetic (EM) energy
As this radiation approaches the Earth, it passes through the atmosphere before reaching the Earth’s surface. What happens to it?
Some is reflected upward from the Earth’s surface, some is absorbed at the surface of the Earth and is then reradiated as thermal energy.
____ Radiation, such as that generated by imaging radars, is also used for remote sensing
Man-Made Radiation
Electromagnetic Radiation consists of ____ which varies in magnitude in a direction perpendicular to the direction of propagation, and ____ which is oriented at right angles to the electrical field and is propagated in phase with the electrical field.
Electrical field (E), Magnetic field (H)
The distance from one wave crest to the next
Wavelength
Measured as the number of crests passing a fixed point in a given period of time.
Frequency
Equivalent to the height of each peak. Often measured as energy levels (formally known as spectral irradiance), expressed as watts per square meter per micrometer (i.e., as energy level per wavelength interval).
Amplitude
Specifies the extent to which the peaks of one waveform align with those of another. Measured in angular units, such as degrees or radians.
Phase (of a waveform)
If two waves are aligned, they oscillate together and are said to be ____? (a phase shift of 0 degrees).
In Phase
If a pair of waves are aligned such that the crests match with the troughs, they are said to be ____?
Out of Phase
Which spectrum, from 0.30 to 15 µm, defines those wavelengths that can be reflected and refracted with lenses and mirrors.
Optical Spectrum
Which spectrum extends from about 0.38 to 3.0 µm; it defines that portion of the solar spectrum used directly for remote sensing.
Reflective Spectrum
Radiation of significance for remote sensing can be said to begin with the ____ region, a zone of short-wavelength radiation that lies between the X-ray region and the limit of human vision. Means “beyond the violet”. Since it’s easily scattered by the Earth’s atmosphere, it is not generally used for remote sensing of Earth materials.
Ultraviolet / Ultraviolet Radiation
The ____ of an object is defined by the color of the light that it reflects
Color