radiation quiz

Question 1

what is radiant energy (or radiation)?

Answer 1

energy transfer via electromagnetic waves

Question 2

what are electromagnetic waves?

Answer 2

radiation waves that have magnetic and electrical properties

Question 3

what is wavelength?

Answer 3

the distance measured along a wave from one crest to another

Question 4

what does radiation not require to move?

Answer 4

a medium

Question 5

how fast does radiation travel?

Answer 5

“speed of light”
3 x 10^8 ms^-1 or 671,000,000 mph

Question 6

what are blackbodies?

Answer 6

hypothetical bodies that absorb & emit max radiation at every wavelength

Question 7

how do the sun, earth, and the atmosphere compare to being blackbodies?

Answer 7

sun & earth close, but not atmosphere (good thing)

Question 8

what is the Stefan-Boltzmann law?

Answer 8

• describes energy emitted based on its temperature
• I = σT^4

Question 9

what is Wien’s law?

Answer 9

• details the wavelength of peak emission of a body based on its temperature
• λmax = b / T

Question 10

** (T OR F) based on how clouds impact radiation in the atmosphere, we can also consider liquid water to have a strong greenhouse effect

Answer 10

FALSE

Question 11

what is scattering?

Answer 11

diffuse radiation

Question 12

what is rayleigh?

Answer 12

short wavelengths
gases in atmosphere
all directions

Question 13

what is mie?

Answer 13

all wavelengths equally
forward primarily
aerosols

Question 14

what is non-selective?

Answer 14

larger particles
all directions

Question 15

what has high albedo?

Answer 15

snow, clouds, venus, ice

Question 16

what has low albedo?

Answer 16

water, moon, forest, fields (dry and plowed)

Question 17

what is albedo?

Answer 17

the percent of reflected solar radiation

Question 18

what is the radiative equilibrium?

Answer 18

absorption = emission

Question 19

what is earth’s radiative equilibrium temp.?

Answer 19

255K
(much cooler than mean of 290K)

Question 20

** of the following, which is arguably the BEST method to keeping a car colder on a hot sunny summer day?

Answer 20

park in the shade !!

Question 21

how does radiation produce heat?

Answer 21

energy (photons) hit molecules and get absorbed, finally adding motion to the molecules (heat from a fire)

Question 22

what is conduction?

Answer 22

transfer of kinetic heat directly from one molecule to another

Question 23

what is convection?

Answer 23

vertical air motions

Question 24

what is advection?

Answer 24

horizontal air motions (caused by wind)

Question 25

why is the atmosphere not a blackbody?

Answer 25

it’s selective

Question 26

what is earth’s peak wavelength?

Answer 26

10 micrometers

Question 27

what is the sun’s peak wavelength?
is it shorter or longer than earth’s?

Answer 27

0.5 micrometers
it is shorter

Question 28

what are selective absorbers?

Answer 28

objects such as gases in the atmosphere that selectively absorb and emit radiation (Kirchhoff’s Law)

Question 29

what is the greenhouse effect?

Answer 29

the atmosphere selectively absorbs infrared radiation from the earth’s surface but acts as a window and transmit shortwave radiation

Question 30

what is an atmospheric window?

Answer 30

exists between 8-13 micrometers where very little infrared radiation is absorbed by the atmosphere (allows for some of earth’s emitted radiation to escape directly to space)

Question 31

what do clouds do to atmospheric windows?

Answer 31

“close” them

Question 32

why is the sky blue?

Answer 32

rayleigh scatters incoming short wave radiation and causes our eyes to see blue

Question 33

why is are sunsets sometimes red, orange, or yellow?

Answer 33

light from the sun has a longer distance to travel which will make the shorter wavelengths dissipate and leave the longer waves

Question 34

why is the sky purple, light blue, or white?

Answer 34

• scattering causes wavelengths to become shorter which leaves purple and blue
• Mie makes the sky white because it allows all wavelengths

Question 35

why are clouds white?

Answer 35

cloud droplets are much larger than air molecules and do not selectively scatter sunlight