Section 3.2 Flashcards

1
Q

True or false

Light is a wave, not a particle

A

False, light has both wave like properties and particle properties

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2
Q

What is the fundamental unit of light?

A

Photon

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3
Q

True or false

Photons have mass

A

False

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4
Q

True or false

Photons travel at the speed of light through the vacuum of space

A

True

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5
Q

Electric and magnetic fields lay ______ to each other

A

Perpendicular

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6
Q

Identify the variables:

c = lamda / v

A
C = speed of light (constant)
V = frequency
Lamda = wavelength
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7
Q

Short wavelengths have _______ frequency

A

High

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8
Q

In terms of waves what is a crest?

A

The peak of a wave

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9
Q

In terms of a wave what is the trough?

A

The low point of a wave

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10
Q

In terms of a wave what is amplitude?

A

The distance from the centre line to the crest or trough.

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11
Q

In terms of a wave what is the wavelength?

A

The distance between two crests

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12
Q

In terms of a wave what is the period?

A

The time it takes a wave to pas a stationary point.

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13
Q

In terms of a wave what is frequency?

A

The amount of waves that pass a stationary point in a set period of time

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14
Q

Microwaves have wavelengths of …..

A

0.1 to 100 cm

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15
Q

Radio wavelengths are ….

A

100cm +

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16
Q

Gamma rays and x-rays are ______ frequency

A

High

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17
Q

Wavelengths lower than 0.4 mm are …..

A

UV rays

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18
Q

Visible light is approximately from _____ to ______ micrometers in wavelength

A

0.4, 0.7

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19
Q

The earth emits ________ radiation.

A

Infrared

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20
Q

Define a blackbody.

A

An object that absorbs all incoming radiation and emits all energy at full efficiency in all wavelengths

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21
Q

True or false

Objects above absolute zero emit electromagnetic radiation.

A

True

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22
Q

Most examples of blackbody objects are a _______ source

A

Thermal

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23
Q

The source of earths electromagnetic radiation is the…..

A

Sun

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24
Q

True or false

A television, lightning and fluorescent light are all examples of blackbody radiation.

A

False

25
Q

Give two examples of blackbody radiation.

A

Burner on electric stove

Incandescent light bulb

26
Q

What scientist is related to blackbody radiation?

A

Max Planck

27
Q

What is Wien displacement law?

A

The wavelength that yields the most radiation can be calculated for a given temperature

28
Q

The solar peak of radiation is in the ________ wavelengths

A

Visible

29
Q

Define irradiance.

A

The radiant flux that is incident on a surface

30
Q

Define radiance.

A

The total amount of energy measured by a sensor in a given direction representing a grounded point

31
Q

Define reflectance.

A

The true image a sensor picks up, taking a radiant image and removing interferences like atmospheric scattering

32
Q

What is transmittance in the atmosphere?

A

Some radiation penetrates a specific surface of a specific material and slows down…. Bending light

33
Q

What is atmospheric absorption?

A

Particles absorb radiation and could possibly re-emit it in a longer wavelength.

34
Q

What is atmospheric reflection and scattering?

A

Surface angle and texture determines if radiation is reflected 180 deg or scattered in numerous directions

35
Q

All forms of remote sensing rely on part of the ….

A

Electromagnetic spectrum

36
Q

What are the three types of atmospheric scattering?

A

Rayleigh
Mie
Non selective

37
Q

Define Rayleigh scattering.

A

Scattering which occurs when the size of the particles is smaller than the wavelength of light.

38
Q

Define Mie scattering.

A

It is another term for non molecular scattering. It is when there is sufficient quantity of materials with diameters 0.1 to 10 times the wavelength of light

39
Q

What is non selective scattering?

A

It is the most problematic of the atmospheric scattering and only occurs in the lower portion of the atmosphere

40
Q

What type of scattering accounts for blue light in the sky?

A

Rayleigh scattering

41
Q

What accounts for the red light in the sky?

A

Rayleigh and Mie scattering

42
Q

What are the most common effects of non selective scattering?

A

Fog and cloud

43
Q

Scattering leads to ______ in an image.

A

Path radiance

44
Q

What does path radiance add to an image?

A

Noise and a washed out image

45
Q

What happens when the AFOV is larger than the depth of the atmospheric column?

A

Lots of noise is generated at the edges of the image

46
Q

Define reflection.

A

The process where energy interacts with an object and bounces back off an object

47
Q

What are the two types of reflection?

A

Diffuse (lambertian)

Specular

48
Q

Define reflectance.

A

The fraction of incident energy that is reflected by a surface that is quantifiable

49
Q

What is the difference between reflectance and reflection.

A

Reflection is the process and reflectance is the fraction measure that is comparable

50
Q

What is a diffuse (lambertian) reflector?

A

Rough surfaces that reflect uniformly in all directions.

51
Q

What is a specular reflector?

A

A mirror like surface where the angle of reflection is equal to the angle of incidence

52
Q

What is the term to describe a surface that is both specular and diffuse?

A

Bidirectional reflectance

53
Q

Name five things that could influence the signal from a bidirectional reflector.

A
Illumination
Sensor
Vegetation
Understory
Soil
54
Q

Define refraction.

A

The bending of light that occurs as light goes through a material. This happens because the speed of light changes

55
Q

Most remote sensing systems collect _______.

A

Reflected radiation

56
Q

What is a spectral signature?

A

The amount of solar radiation transmitted in a wavelength. These help us identify materials. This can also be called a spectral curve

57
Q

What is a feature space?

A

Using two or more wavelengths and the spectral signature is plotted in a multidimensional space

58
Q

How does the amount of rejected energy distinguish between surfaces?

A

Different surfaces absorb and reflect different wavelengths and looking at the spectral signature can help distinguish these