Emitting And Absorbing Radiation

Question 1

what are all objects doing

Answer 1

continuously emitting and absorbing em radiation over a range of wavelengths

Question 2

what does the distribution and intensity of emitted wavelengths depend on

Answer 2

• the objects temperature

- so intensity is the power unit area

Question 3

what happens as the temperature of an object increases

Answer 3

the intensity of every emitted wavelength increases

Question 4

what does the intensity increase more rapidly for in terms of radiation

Answer 4

• shorter wavelengths than longer wavelengths

- this causes the peak wavelength to decrease

Question 5

what happens in the average power that an object absorbs is more than the average power it radiates

Answer 5

the object heats up

Question 6

when does an object cool down

Answer 6

when the average power emitted is more than than the power absorbed

Question 7

an object that remains at a constant temperature…

Answer 7

radiates and absorbs the same average power

Question 8

what does the overall temperature of the earth depend on

Answer 8

the amount of radiation ti reflects, absorbs and emits

Question 9

what happens to the radiation from the sun being transferred from the earth to the sun

Answer 9

• some of it is reflected, but most of it is absorbed
• the radiation of reflected and absorbed by the earth’s atmosphere, clouds and surface
• this causes an increase in the local temperature

Question 10

why is there a decrease in the earth’s local temperature at night

Answer 10

• because radiation is emitted by the atmosphere, clouds and the surface of the earth
• so overall, the temperature of the earth remains fairly constant

Question 11

what can changes to the atmosphere cause and how

Answer 11

• a change to the earth’s overall temperature
• if the atmosphere starts to absorb more radiation without emitting the same amount
• the overall temperature will rise until absorption and emission are equal again (global warming)

Question 12

what is the experiment for investigating how well different surfaces emit radiation

Answer 12

• wrap four identical test tubes with material like paper
• the material covering each test tube should be the same, but a different colour (black to white)
• boil water in a test tube and fill each tube with same volume
• use a thermometer to measure the temp of the water in the test tubes everyh minute
• seal the test tubes with bungs between measurements

Question 13

what would your findings be in the experiment investigating radiation emittion

Answer 13

• the temperature of water will decrease quicker for the test tube surrounded by surfaces that are good emitters of radiation
• so you should find that matte surfaces are better emitters than shiny ones
• and that black surfaces emit radiation better than white ones