Chapter 3

Question 1

What is power?

Answer 1

rate at which energy is flowing
expressed in watts

Question 2

What is internal energy?

Answer 2

how fast the atoms and molecules in the object are moving

Question 3

What is temperature?

Answer 3

measure of internal energy of an object

Question 4

What are most temps of earth in K?

Answer 4

200k to 300k

Question 5

How is energy transported from the sun to the earth?

Answer 5

electromagnetic radiation

Question 6

What are the wavelengths of visible photons?

Answer 6

.4-.8 microns

Question 7

What is Wien’s displacement law?

Answer 7

relation between an object’s temp and the peak of its emission spectrum

Question 8

What is the Wien’s displacement equation?

Answer 8

λmax=2897/T

Question 9

How does a lightbulb produce a higher fraction of visible photons?

Answer 9

run the filament at a higher temp

Question 10

What is the meaning of the Stefan-Boltzmann equation?

Answer 10

total power radiated by a blackbody temp

Question 11

What is the Stefan-Boltzmann equation?

Answer 11

P/a=σT^4

Question 12

What is P/a?

Answer 12

power emitted by a blackbody per unit of surface area (w/m^2)

Question 13

What is the Stefan-Boltzmann constant?

Answer 13

σ=5.67x10^-8 w/m^2/K^4

Question 14

What is the 1st law of thermodynamics?

Answer 14

energy is conserved

Question 15

What happens when energy in is greater than energy out?

Answer 15

internal energy and temp increase

Question 16

What happens when energy out is greater than energy in?

Answer 16

internal energy and temp decrease

Question 17

What happens when energy in equals energy out?

Answer 17

internal temp and energy don’t change: equilibrium

Question 18

What are blackbodies?

Answer 18

body or surface that completely absorbs all radiant energy that falls upon it with no reflection
Surface that emits photons but we can’t see them

Question 19

How can energy move?

Answer 19

energy can be absorbed, transmitted, reflected, or emitted

Question 20

Can most infrared wavelengths pass through the atmosphere?

Answer 20

no, the atmosphere does not let eaves through equally (blocks some)

Question 21

Does all visible light pass through the atmosphere?

Answer 21

yes

Question 22

Where do incandescent light bulbs emit light?

Answer 22

1600-6000 K

Question 23

What is thermal energy?

Answer 23

energy of motion

Question 24

What is heat?

Answer 24

thermal energy transferred between 2 bodies with different temperaturese

Question 25

Is there movement at 0 K?

Answer 25

no

Question 26

What happens if there is more than 0 K?

Answer 26

there is movement of molecules

Question 27

What happens if there is movement?

Answer 27

energy is emitted (photons)

Question 28

Why don’t we see light when there is movement?

Answer 28

it is not in our visible range

Question 29

What happens if there is an increase in speed of molecules?

Answer 29

there is light in our visible range

Question 30

What is black?

Answer 30

light we can’t see

Question 31

Where would a perfect blackbody be?

Answer 31

in complete darkness

Question 32

Why do our eyes see blackbodies in light?

Answer 32

the light is reflecting in a range we can see

Question 33

Is Earth a blackbody?

Answer 33

yes

Question 34

What does the atmosphere let through?

Answer 34

visible light

Question 35

What does the atmosphere only let some of through?

Answer 35

infrared radiation

Question 36

Is the atmosphere a blackbody?

Answer 36

yes