8: The Greenhouse Effect

Question 1

What is an example of a black body

Answer 1

A star

Question 2

What are black bodies

Answer 2

Idealized bodies, they emit everything they absorb

Question 3

What is the emissivity of a black body

Answer 3

1

Question 4

What is the modified Stephen Boltzmann’s law to calculate how much real bodies radiate

Answer 4

P=σAT^4

Question 5

What is the emissivity and albedo relation

Answer 5

e+a=1

Question 6

Formula for Inet

Answer 6

Inet= I1- I2

Question 7

What happens to the rays of the sun

Answer 7

The sun is so far away the sun rays basically arrive parallel

Question 8

How do you calculate the power the earth receives?

Answer 8

disc (cross-section of the earth) = A= pi x R^2
The surface area of the earth (4 x pi x R^2)

Question 8

Solar constant formula

Answer 8

P=SA
S=Intensity

Question 9

How is the earth treated when measuring radiation?

Answer 9

As a point without interactions between the surface and atmosphere.

Question 10

What do greenhouse gases do?

Answer 10

Absorb infrared radiation

Question 11

Which are the greenhouse gases?

Answer 11

-Water vapour
-Carbon dioxide
-Methane
-Nitrous oxide.

Question 12

How do you calculate the average intensity over the entire surface of the earth?

Answer 12

Iav= S x pi x r^2 / 4 x pi x r^2
(Iav = S/4)

Question 13

Average intensity of the earth

Answer 13

Iav= (1-a) x S / 4

Question 14

Define the enhanced greenhouse effect

Answer 14

Additional warming due to increased quantities of the greenhouse gases in the atmosphere

Question 15

Mechanism of the absorption of a photon with energy levels

Answer 15

1) Infrared photons absorbed by greenhouse gases
2) Gas molecules that have absorbed the photons get excited, energy level rises
3) Molecules prefer low energy states and they change to this by emitting the photons (not all photons as some stay in the surface).

Question 16

Mechanism of the absorption of a photon with resonance

Answer 16

1) The photo’ns natural frequency is the perfect frequency that greenhous gases can absorb
2) Wavelength ecreases has to be expelled.