Section 3.2 Flashcards
True or false
Light is a wave, not a particle
False, light has both wave like properties and particle properties
What is the fundamental unit of light?
Photon
True or false
Photons have mass
False
True or false
Photons travel at the speed of light through the vacuum of space
True
Electric and magnetic fields lay ______ to each other
Perpendicular
Identify the variables:
c = lamda / v
C = speed of light (constant) V = frequency Lamda = wavelength
Short wavelengths have _______ frequency
High
In terms of waves what is a crest?
The peak of a wave
In terms of a wave what is the trough?
The low point of a wave
In terms of a wave what is amplitude?
The distance from the centre line to the crest or trough.
In terms of a wave what is the wavelength?
The distance between two crests
In terms of a wave what is the period?
The time it takes a wave to pas a stationary point.
In terms of a wave what is frequency?
The amount of waves that pass a stationary point in a set period of time
Microwaves have wavelengths of …..
0.1 to 100 cm
Radio wavelengths are ….
100cm +
Gamma rays and x-rays are ______ frequency
High
Wavelengths lower than 0.4 mm are …..
UV rays
Visible light is approximately from _____ to ______ micrometers in wavelength
0.4, 0.7
The earth emits ________ radiation.
Infrared
Define a blackbody.
An object that absorbs all incoming radiation and emits all energy at full efficiency in all wavelengths
True or false
Objects above absolute zero emit electromagnetic radiation.
True
Most examples of blackbody objects are a _______ source
Thermal
The source of earths electromagnetic radiation is the…..
Sun
True or false
A television, lightning and fluorescent light are all examples of blackbody radiation.
False
Give two examples of blackbody radiation.
Burner on electric stove
Incandescent light bulb
What scientist is related to blackbody radiation?
Max Planck
What is Wien displacement law?
The wavelength that yields the most radiation can be calculated for a given temperature
The solar peak of radiation is in the ________ wavelengths
Visible
Define irradiance.
The radiant flux that is incident on a surface
Define radiance.
The total amount of energy measured by a sensor in a given direction representing a grounded point
Define reflectance.
The true image a sensor picks up, taking a radiant image and removing interferences like atmospheric scattering
What is transmittance in the atmosphere?
Some radiation penetrates a specific surface of a specific material and slows down…. Bending light
What is atmospheric absorption?
Particles absorb radiation and could possibly re-emit it in a longer wavelength.
What is atmospheric reflection and scattering?
Surface angle and texture determines if radiation is reflected 180 deg or scattered in numerous directions
All forms of remote sensing rely on part of the ….
Electromagnetic spectrum
What are the three types of atmospheric scattering?
Rayleigh
Mie
Non selective
Define Rayleigh scattering.
Scattering which occurs when the size of the particles is smaller than the wavelength of light.
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
What is non selective scattering?
It is the most problematic of the atmospheric scattering and only occurs in the lower portion of the atmosphere
What type of scattering accounts for blue light in the sky?
Rayleigh scattering
What accounts for the red light in the sky?
Rayleigh and Mie scattering
What are the most common effects of non selective scattering?
Fog and cloud
Scattering leads to ______ in an image.
Path radiance
What does path radiance add to an image?
Noise and a washed out image
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
Define reflection.
The process where energy interacts with an object and bounces back off an object
What are the two types of reflection?
Diffuse (lambertian)
Specular
Define reflectance.
The fraction of incident energy that is reflected by a surface that is quantifiable
What is the difference between reflectance and reflection.
Reflection is the process and reflectance is the fraction measure that is comparable
What is a diffuse (lambertian) reflector?
Rough surfaces that reflect uniformly in all directions.
What is a specular reflector?
A mirror like surface where the angle of reflection is equal to the angle of incidence
What is the term to describe a surface that is both specular and diffuse?
Bidirectional reflectance
Name five things that could influence the signal from a bidirectional reflector.
Illumination Sensor Vegetation Understory Soil
Define refraction.
The bending of light that occurs as light goes through a material. This happens because the speed of light changes
Most remote sensing systems collect _______.
Reflected radiation
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
What is a feature space?
Using two or more wavelengths and the spectral signature is plotted in a multidimensional space
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
