The nature of electromagnetic radiation part1 Flashcards Preview

Atmospheric remote sensing > The nature of electromagnetic radiation part1 > Flashcards

Flashcards in The nature of electromagnetic radiation part1 Deck (66)
Loading flashcards...
1

Electromagnetic radiation in the atmosphere interacts with

gases, aerosol particles, and cloud particles.

2

Extinction and emission are two main types of

the interactions between an electromagnetic radiation field and a medium (e.g., the atmosphere).

3

Extinction is 

a process that decreases the radiative intensity, while emission increases it.

4

extinction also means

attenuation

5

Radiation is ....................... by ......................................................................................

emitted

all bodies that have a temperature above absolute zero (O K) (often referred to as thermal emission).

6

Extinction is due to

absorption and scattering.

7

Absorption is

a process that removes the radiative energy from an electromagnetic field and transfers it to other forms of energy.

8

Scattering is

a process that does not remove energy from the radiation field, but may redirect it.

9

Scattering can be thought of as ............................of .................................................... 

absorption

radiative energy followed by re- emission back to the electromagnetic field with negligible conversion of energy

 

10

Scattering can be thought of as absorption of radiative energy followed by re- emission back to the electromagnetic field with negligible conversion of energy. Thus,

scattering can remove radiative energy of a light beam traveling in one direction, but can be a “source” of radiative energy for the light beams traveling in other directions.

11

what is the difference between elastic and inelastic scattering

Elastic scattering is the case when the scattered radiation has the same frequency as that of the incident field. Inelastic (Raman) scattering results in scattered light with a frequency different from that of the incident light.

12

Blackbody is

a body whose absorbs all radiation incident upon it.

13

Properties of blackbody radiation:

  • Radiation emitted by a blackbody is isotropic, homogeneous and unpolarized;
  • Blackbody radiation at a given wavelength depends only on the temperature;
  • Any two blackbodies at the same temperature emit precisely the same radiation;
  • A blackbody emits more radiation than any other type of an object at the same temperature;

14

The atmosphere is not strictly in the thermodynamic equilibrium because

its temperature and pressure are functions of position. Therefore, it is usually subdivided into small subsystems each of which is effectively isothermal and isobaric referred to as Local Thermodynamical Equilibrium (LTE).

15

A concept of LTE plays a fundamental role in

atmospheric studies: e.g., the main radiation laws discussed below, which are strictly speaking valid in thermodynamical equilibrium, can be applied to an atmospheric air parcel in LTE.

16

Planck function definition

Bλ(T), gives the intensity (or radiance) emitted by a blackbody having a given temperature.

17

Plank function can be expressed in

wavelength, frequency, or wavenumber domains

18

Plank function can be expressed in wavelength, frequency, or wavenumber domains as

19

what does each symbol mean 

20

The relations between Bv~ (T ); Bv (T ) and Bλ(T ) are derived using that 

21

Explain the graph

the graph shows plancks radiance "emissivity" and wavelength

when temperature of the object is low wavelength is larger and radiance is low 

22

The Stefan-Boltzmann law states that

the radiative flux emitted by a blackbody, per unit surface area of the blackbody, varies as the fourth power of the temperature.

23

Stefan-Boltzmann law formula

24

explain the terms in Stefan-Boltzmann law

25

Wien’s displacement law

 states that the wavelength at which the blackbody 
emission spectrum is most intense varies inversely with the blackbody’s temperature.

26

The Wien’s displacement law states that the wavelength at which the blackbody 
emission spectrum is most intense varies inversely with the blackbody’s temperature. The 
constant of proportionality is

Wien’s constant(2897 K µm): 
λm= 2897 / T 

27

Explain the terms of weins displacement law

where λm is the wavelength (in micrometers, µm) at which the peak emission intensity 
occurs, and T is the temperature of the blackbody (in degrees Kelvin, K)

28

Wein's displacement law is simply derived from

 dBλ/dλ= 0

29

Wien's displacement law (easy to remember statement)

The hotter the object the shorter the wavelength of the maximum intensity emitted

30

Kirchhodd's law

states that the emissivity ελ, of a medium is equal to the 
absorptivity, Αλ, of this medium under thermodynamic equilibrium

ελ= Αλ