black body radiation- emission & absorption of inferred radiation.

Question 1

explain why matte black objects get warmer than shiny objects in the sun.

Answer 1

matte black absorbs more infra-red energy than shiny ones.

Question 2

why does black look black?

Answer 2

• absorbs all em radiation incident on it.
• reflects no em radiation incident on it.
• best possible emitter.

Question 3

kelvin scale: what happens to the intial energy and temperature of a substance when energy is removed?

Answer 3

decreases.

Question 4

kelvin scale: what if all the internal energy is removed?

Answer 4

temeprature can’t go any lower, this is known as zero kelvin or absolute zero.

Question 5

kelvin scale: what is 0k = to?

Answer 5

-273 degress centigrade.

Question 6

kelvin scale: what is 0 degrees centigrade equal to?

Answer 6

273k.

Question 7

black body radiation: if a pan is cold and more thermal radiation is absorbed than emitted what happens to the temperature of the pan?

Answer 7

increases.

Question 8

black body radiation: if the pan is getting warmer what has happend to the amount of thermal radiation and what is that still less than? the temperature will continue to increase but what will happend to the rate of increase?

Answer 8

increase.
decrease.

Question 9

black body radiation: if the pan is hot the amount of thermal radiation emitted by the pan is what to that being absorbed and what happens to the pans temperature?

Answer 9

equal.
remains constant.

Question 10

what do all bodies emitt?

Answer 10

thermal radiation.

Question 11

the hotter the body the greater the what?

Answer 11

intensity of the emitted radiation.

Question 12

what does the peak wavelength of the emitted radiation decrease with? what does this sugegst about hot objects?

Answer 12

increasing temeprature.
why they glow red whilst very hot ones are said to be white hot.

Question 13

green house effect: what is blackbody radiation?

Answer 13

objects that emit electromagnetic energy.

Question 14

green house effect: what objects radiate their radiation at short wavelengths?

Answer 14

hot objects.
eg: sun.

Question 15

green house effect: what have our eyes evolved to do?

Answer 15

most sensitive at the wavelngth corrrospounding to the peak in this radiation which is the visiable part of the electromagnetic spectrum.

Question 16

green house effect: what kind of objects emit their energy at longer wavelengths?

Answer 16

colder objects.
eg: earth.

Question 17

green house effect: what is the number of wavelngths that carbon diode absorbs its energy at?

Answer 17

4.3 and 15 microns.

Question 18

green house effect: what is thermal radiation emitted by?

Answer 18

the sun.

Question 19

green house effect: due to the sun being very hot what does that mean for its radiation?

Answer 19

is at short wavelngths and very little of the energy is absorbed by the carbon dioxide in the atmosphere.

Question 20

green house effect: what is the radiation from the sun absorbed by and what does this cause?

Answer 20

surface of the earth.
increases its temperature.

Question 21

green house effect: what does the surface of the earth emit?

Answer 21

black body radiation.

Question 22

green house effect: due to the earth being much cooler than the sun how is its radiation emitted?

Answer 22

at long wavelengths.

Question 23

green house effect: what happens to the radiation emitted by earth and what does it lead to?

Answer 23

absorbed by carbon dioxide in the atomsphere. temperature icnrease in the temperature of the atmosphere.