Thermal Energy Transfer (DP IB Physics: SL)

Objects with absolute temperature can lose energy through

1. convection
2. conduction
3. radiation

Equipment is tested on Earth for use on the surface of Mars. How will the equipment lose energy in the two locations?

The average albedo of desert sand is 0.4. What is the ?

The black body temperature of Venus is 90% of the black body temperature of Earth.

Which of the following correctly shows the ratio:

Which factors affect the amount of solar power incident on a given point on the surface of the Earth? 

1. Weather conditions
2. Latitude
3. Position of the Moon in its orbit of the Earth
4. Position of the Earth in its orbit of the Sun

A black body has absolute temperature T and surface area A. The total power radiated by the body is P. What is the value of power if the surface area is reduced to one third of A, and the temperature increased to three times T?

A graph is plotted to show the variation of intensity I and wavelength of emitted radiation λ. Cool objects are represented by a dashed line, and hotter objects are represented by a solid line.

Which graph correctly shows the relationship between I and λ?

The solar constant is quoted as an average rather than an absolute value. Which statements correctly explain this? 

1. The Earth follows an elliptical orbit around the Sun
2. The Earth rotates on an axis which is tilted at 23.5^o to the plane of its orbit
3. The energy output of the Sun varies according to an 11-year cycle

Certain gases, for example carbon dioxide and methane, are categorised as greenhouse gases. This is because they:

Some of the energy incident on the surface of the Earth is emitted as infrared radiation. Why does this cause a ‘greenhouse effect’?

The peak wavelength of two lamps are compared. The first lamp has a filament in a vacuum with a temperature of 1200 K under normal working conditions. The second similar lamp is gas-filled and has a filament temperature of 2400 K.

What is an estimate for the ratio of the wavelength at which the maximum intensity of radiation is emitted by the vacuum lamp and the gas-filled lamp?

A black body has a total power radiated P and a surface area A. The surface area is reduced to one-quarter of A and the total power is increased to four times P.

What is the value of the peak wavelength?

The radiation emitted from an asteroid is monitored and the following spectrum is obtained. 

Which of the following is a sensible estimate for the temperature of the asteroid. 

The sun behaves as an approximate black-body radiator with peak energy radiation occurring at wavelength 51 × 10⁻⁸ m and a power of 4 × 10²⁶ W.

What is the correct expression for the radius of the Sun?

Rigel A in the constellation of Orion is a massive blue variable star with a peak wavelength of 0.25 μm. 

Which of the graphs shows the intensity of radiation emitted by Rigel A against the wavelength of that radiation? 

A double-glazed window filled with argon has an area of 3 m². The outdoor temperature is 8 °C and the indoor temperature 21 °C. 

What is the rate of heat loss in watts through the window? 

The diagram shows a simplified model of the energy balance of the Earth. 

What is the albedo of the Earth according to this model?

During a freak weather event, the average intensity of light received on Earth was 5 × 10⁻⁵r W m⁻². r is the radius of the Sun equal to 7 × 10⁸ m.  The average albedo was 0.8 and the average emissivity was . The light coming from the Sun to the Earth travels through a total area of 1 × 10¹⁷ m². 

Assume that σ = 6 × 10⁻⁸ W m⁻² K⁻⁴ 

What was the average temperature of the Earth during the event?