3.11 Energy and the environment (option)

Question 1

Describe how greenhouse gases trap heat in the atmosphere

Answer 1

• Sun radiates short wavelength IR which reaches Earth’s atmosphere
• Atmospheric layer traps rays and heats up; some of these rays go through the layer and heat the planet
• Soil and water reflect / re-radiate long wavelength IR which cannot escape the atmosphere

Question 2

Which 4 gases contribute to the greenhouse effect?

Answer 2

• Water vapour
• Carbon dioxide
• Methane
• Ozone

Question 3

How much of the power from the sun is absorbed by the Earth and its atmosphere?

Answer 3

Approximately 70%

Question 4

What are the 5 main types of human activity that have increased the concentration of greenhouse gases int he atmosphere?

Answer 4

• Industrial activity
• Transport
• Cattle
• Deforestation
• Farming

Question 5

What form is solar energy transmitted in?

Answer 5

Electromagnetic radiation

Question 6

What is the greenhouse effect?

Answer 6

The process of the warming of a planet by radiation from its atmosphere to a temperature above what it would be without an atmosphere

Question 7

How much of the energy of solar radiation is contained within the band of the EM spectrum between UV and IR?

Answer 7

99%

Question 8

What is Wien’s law?

Answer 8

The higher the temperature, the smaller the wavelength at which the radiation curve reaches its maximum - peak wavelength is inversely proportional to temperature

Question 9

What is the Stefan-Boltzmann law?

Answer 9

The energy radiated from a black body is proportional to the 4th power of the absolute temperature - P = A(sigma)(T^4)

Question 10

What is the composition of the atmosphere?

Answer 10

• Nitrogen: 78.08%
• Oxygen: 20.95%
• Argon: 0.93%
• Carbon dioxide: 0.04%
• Other trace gases

Question 11

What is the solar constant, G?

Answer 11

The solar constant is the radiative power per unit area incident on a surface at right angles to solar radiation, at the surface of the earth the value of G is 1.36 kWm^-2

Question 12

What is Archimedes’ principle?

Answer 12

The upward buoyant force on a body immersed in a fluid is equal to the weight of fluid that the body displaces - F = (rowe)gV

Question 13

How do ice caps and icebergs melting affect rising sea levels?

Answer 13

• Ice caps: Displace water and increase the sea level
• Icebergs: Do not increase the sea level through melting as they are already displacing the water beforehand

Question 14

What equation allows you to calculate intensity of light from the sun?

Answer 14

I = P/A where A is the surface area - this is an inverse square law

Question 15

What is the main source of energy from the sun?

Answer 15

The proton-proton chain fusion reaction, where 4 hydrogen nuclei combine to create a helium nucleus, releasing gamma rays

Question 16

What is the equation for electrical energy from a PV cell?

Answer 16

Electrical energy = Light energy x (cell efficiency / 100), where cell efficiency = (useful energy output / total energy input) x 100

Question 17

What are the 2 ways a molecule can de-excite?

Answer 17

• Collision with another molecule, increasing the kinetic energy of the molecules
• Re-radiation - can occur in any direction so approximately 50% of re-radiated photons will be absorbed by the ground

Question 18

What is the difference between a renewable and a non-renewable energy source?

Answer 18

A renewable energy source can be naturally replenished within a human lifetime whereas a non-renewable source is regarded as incapable of replenishment

Question 19

What is a main sequence star?

Answer 19

A star which generates the majority of its energy through nuclear fusion of hydrogen to helium at its core