Electromagnetic Spectrum

Question 1

Objects also _____ that has been emitted by other objects.

Answer 1

Reflect radiation

Question 1

All objects emit __? Except objects at __?

Answer 1

Electromagnetic Radiation, Absolute Zero

Question 2

The most familiar form of Electromagnetic Radiation

Answer 2

Visible Light

Question 3

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

Answer 3

Electromagnetic (EM) energy

Question 4

As this radiation approaches the Earth, it passes through the atmosphere before reaching the Earth’s surface. What happens to it?

Answer 4

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.

Question 5

____ Radiation, such as that generated by imaging radars, is also used for remote sensing

Answer 5

Man-Made Radiation

Question 6

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.

Answer 6

Electrical field (E), Magnetic field (H)

Question 7

The distance from one wave crest to the next

Answer 7

Wavelength

Question 8

Measured as the number of crests passing a fixed point in a given period of time.

Answer 8

Frequency

Question 9

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).

Answer 9

Amplitude

Question 10

Specifies the extent to which the peaks of one waveform align with those of another. Measured in angular units, such as degrees or radians.

Answer 10

Phase (of a waveform)

Question 11

If two waves are aligned, they oscillate together and are said to be ____? (a phase shift of 0 degrees).

Answer 11

In Phase

Question 12

If a pair of waves are aligned such that the crests match with the troughs, they are said to be ____?

Answer 12

Out of Phase

Question 13

Which spectrum, from 0.30 to 15 µm, defines those wavelengths that can be reflected and refracted with lenses and mirrors.

Answer 13

Optical Spectrum

Question 14

Which spectrum extends from about 0.38 to 3.0 µm; it defines that portion of the solar spectrum used directly for remote sensing.

Answer 14

Reflective Spectrum

Question 15

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.

Answer 15

Ultraviolet / Ultraviolet Radiation

Question 16

The ____ of an object is defined by the color of the light that it reflects

Answer 16

Color

Question 17

Limits of the ____are defined by the sensitivity of the human visual system

Answer 17

Visible Spectrum

Question 18

Primary Colors (Answer based on wavelength): 0.4 to 0.5 µm, 0.5 to 0.6 µm, 0.6 to 0.7 µm

Answer 18

Blue, Green, Red

Question 19

Equal proportions of the three additive primaries combine to form what?

Answer 19

White / White light

Question 20

Each of the three subtractive primaries absorbs a third of the visible spectrum (Color Absence). Yellow absorbs ____, Cyan absorbs ____, and Magenta absorbs ____?

Answer 20

Blue, Red, Green

Question 21

A mixture of equal proportions of pigments of the three subtractive primaries yields ___?

Answer 21

Black

Question 22

Wavelengths longer than the red portion of the visible spectrum are designated as the ___? It extends from 0.72 to 15 µm—making it more than ____ times as wide as the visible light spectrum.

Answer 22

Infrared / Infrared Region, 40

Question 23

Defined as those regions of the infrared spectrum closest to the visible. Can use films, filters, and cameras with designs similar to those intended for use with visible light. Essentially solar radiation reflected from the Earth’s surface

Answer 23

Near Infrared and Mid Infrared radiation

Question 24

Consisting of wavelengths well beyond the visible, extending into regions that border the microwave region, emitted by the Earth. Consists of “heat,” or “thermal energy”.

Answer 24

Far Infrared / Far Infrared Region

Question 25

In this region, the longest wavelengths commonly used in remote sensing are those from about 1 mm to 1 µm in wavelength. The shortest wavelengths in this range have much in common with the thermal energy of the far infrared. The longer wavelengths of this region merge into the radio wavelengths used for commercial broadcasts.

Answer 25

Microwave / Microwave Region

Question 26

Planck discovered that electromagnetic energy is absorbed and emitted in discrete units called ____? The size of each unit is directly proportional to the ____ of the energy’s radiation.

Answer 26

Quanta or Photons, Frequency

Question 27

The generation of electric currents by the exposure of certain substances to light, as the effect of the impact of these discrete units of energy (quanta) on surfaces of certain metals, causing the emission of electrons.

Answer 27

Photoelectric Effect

Question 28

Made the wave model of electromagnetic radiation.

Answer 28

James Clerk Maxwell

Question 29

Based on the assumption from classical (mechanical) physics that light and other forms of electromagnetic energy propagate as a series of waves. Best explains some aspects of the observed behavior of electromagnetic energy (e.g., refraction by lenses and prisms and diffraction), whereas quantum theory provides explanations of other phenomena (notably, the photoelectric effect).

Answer 29

Wave Model

Question 30

The rate at which photons (quanta) strike a surface. Measured in Watts (W)

Answer 30

Radiant Flux (Fe)

Question 31

____ measures radiation that strikes a surface, _____ defines the rate at which radiation is emitted from a unit area (also measured in watts per square meter)

Answer 31

Irradiance, Radiant Exitance

Question 32

All objects with temperatures above absolute zero have _____ and ____ energy.

Answer 32

Temperature, Emit

Question 33

The amount of energy and the wavelengths at which it is emitted depend on the ____ of the object.

Answer 33

Temperature

Question 34

As the temperature of an object increases, the total amount of energy emitted also _____, and the wavelength of maximum (peak) emission becomes ______.

Answer 34

Increases, Shorter

Question 35

A _____ is a hypothetical source of energy that behaves in an idealized manner. It absorbs all incident radiation; none is reflected. Emits energy with perfect efficiency. A hypothetical entity because in nature all objects reflect at least a small proportion of the radiation that strikes them and thus do not act as perfect reradiators of absorbed energy.

Answer 35

Blackbody

Question 36

_____ states that the ratio of emitted radiation to absorbed radiation flux is the same for all blackbodies at the same temperature.

Answer 36

Kirchhoff’s Law

Question 37

The emissivity of a true blackbody is __, and that of a perfect reflector (a whitebody) would be ___.

Answer 37

1, 0

Question 38

_____ is a useful measure of their effectiveness as radiators of electromagnetic energy. Those objects that tend to absorb high proportions of incident radiation and then to reradiate this energy will have high ones and vice versa.

Answer 38

Emissivity

Question 39

Defines the relationship between the total emitted radiation (W) (often expressed in watts · cm–2) and temperature (T) (absolute temperature, K).

Answer 39

Stefan–Boltzmann Law

Question 40

S-B law states that ___ blackbodies emit more energy per unit area than do ___ blackbodies.

Answer 40

Hot, Cool

Question 41

Specifies the relationship between the wavelength of radiation emitted and the temperature of a blackbody.

Answer 41

Wien’s Displacement Law

Question 42

According to Wien’s Displacement Law, as blackbodies become ____, the wavelength of maximum emittance shifts to _____ wavelengths.

Answer 42

Hotter, Shorter