Section 3.2 Flashcards Preview

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Flashcards in Section 3.2 Deck (58):
1

True or false
Light is a wave, not a particle

False, light has both wave like properties and particle properties

2

What is the fundamental unit of light?

Photon

3

True or false
Photons have mass

False

4

True or false
Photons travel at the speed of light through the vacuum of space

True

5

Electric and magnetic fields lay ______ to each other

Perpendicular

6

Identify the variables:

c = lamda / v

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

7

Short wavelengths have _______ frequency

High

8

In terms of waves what is a crest?

The peak of a wave

9

In terms of a wave what is the trough?

The low point of a wave

10

In terms of a wave what is amplitude?

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

11

In terms of a wave what is the wavelength?

The distance between two crests

12

In terms of a wave what is the period?

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

13

In terms of a wave what is frequency?

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

14

Microwaves have wavelengths of .....

0.1 to 100 cm

15

Radio wavelengths are ....

100cm +

16

Gamma rays and x-rays are ______ frequency

High

17

Wavelengths lower than 0.4 mm are .....

UV rays

18

Visible light is approximately from _____ to ______ micrometers in wavelength

0.4, 0.7

19

The earth emits ________ radiation.

Infrared

20

Define a blackbody.

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

21

True or false
Objects above absolute zero emit electromagnetic radiation.

True

22

Most examples of blackbody objects are a _______ source

Thermal

23

The source of earths electromagnetic radiation is the.....

Sun

24

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

False

25

Give two examples of blackbody radiation.

Burner on electric stove
Incandescent light bulb

26

What scientist is related to blackbody radiation?

Max Planck

27

What is Wien displacement law?

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

28

The solar peak of radiation is in the ________ wavelengths

Visible

29

Define irradiance.

The radiant flux that is incident on a surface

30

Define radiance.

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

31

Define reflectance.

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

32

What is transmittance in the atmosphere?

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

33

What is atmospheric absorption?

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

34

What is atmospheric reflection and scattering?

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

35

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

Electromagnetic spectrum

36

What are the three types of atmospheric scattering?

Rayleigh
Mie
Non selective

37

Define Rayleigh scattering.

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

38

Define Mie scattering.

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

What is non selective scattering?

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

40

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

Rayleigh scattering

41

What accounts for the red light in the sky?

Rayleigh and Mie scattering

42

What are the most common effects of non selective scattering?

Fog and cloud

43

Scattering leads to ______ in an image.

Path radiance

44

What does path radiance add to an image?

Noise and a washed out image

45

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

Lots of noise is generated at the edges of the image

46

Define reflection.

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

47

What are the two types of reflection?

Diffuse (lambertian)
Specular

48

Define reflectance.

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

49

What is the difference between reflectance and reflection.

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

50

What is a diffuse (lambertian) reflector?

Rough surfaces that reflect uniformly in all directions.

51

What is a specular reflector?

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

52

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

Bidirectional reflectance

53

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

Illumination
Sensor
Vegetation
Understory
Soil

54

Define refraction.

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

55

Most remote sensing systems collect _______.

Reflected radiation

56

What is a spectral signature?

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

57

What is a feature space?

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

58

How does the amount of rejected energy distinguish between surfaces?

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