Assume that the distance d between the sun and the earth decreases. Then the Earth's average temperature will go up. The fraction of the power radiated by the Sun that is received on Earth is proportional to 1 d 2 , the power radiated by the earth is proportional to T 4 . Deduce the dependence of the temperature T of the earth is proportional to the distance between the sun and the earth.

The power radiated by earth is proportional to the power received from the sun, and since the power received from the sun is inversely proportional to d 2 , so will be the power radiated by the earth. Now, the power radiated is described as ( σ A T 4 ) ,hence we can write the following, σ A T 4 ∝ 1 d 2 since σ , A are constants, then T 4 ∝ 1 d 2 T ∝ 1 d

E M B I B E

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 27

EASY

Diploma

IMPORTANT

Earn 100

Suggest whether there is any point in using a ceiling fan in winters?

Important Questions on Energy Production

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 28

Calculate the ratio of power radiated per unit area from two black bodies at temperature

900 K

and

300 K

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 29

State what do understand by the term black body.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 29

Give an example of a black body which is a good approximation to a ideal black body.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 29

By what factor does the rate of radiation from a body increase when the temperature is increased from

50^{\circ} C t o 100^{\circ} C

.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 30

The graph shows variation with wavelength of the intensity of radiation emitted by two bodies of identical shapes.

Question Image

Explain why the temperature of the two bodies is the same?

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 30

The graph shows variation with wavelength of the intensity of radiation emitted by two bodies of identical shapes.

Question Image

If the upper line corresponds to a black body.Calculate the emissivity of the other body.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 31

The total power radiated by a body of area

5.00 k m^{2}

and emissivity

0.800

is

1.35 \times 10^{9} W

. Assume that the body radiates into a vacuum at temperature

0 K

.Calculate the temperature (in Kelvin) of the body.

EASY

Diploma

IMPORTANT

Physics for the IB Diploma 6th Edition>Chapter 8 - Energy Production>Test yourself>Q 32

Assume that the distance

d

between the sun and the earth decreases. Then the Earth's average temperature will go up. The fraction of the power radiated by the Sun that is received on Earth is proportional to