Chapter 16 Heat Transfer. Topics: Conduction Convection Radiation Greenhouse Effect/Global Warming

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1 Chapter 16 Heat Transfer Topics: Conduction Convection Radiation Greenhouse Effect/Global Warming

2 Radiation Every object at a temperature above absolute zero is an emitted of electromagnetic radiation Electromagnetic radiation are waves that travel at the speed of light. The frequency and wavelength of the waves are related by f λ = c The full electromagnetic spectrum

3 Which arrangement of types of electromagnetic waves is in the correct order of increasing frequency? A. Radio waves, ultra-violet light, x-rays, visible light B. X-rays, ultra-violet light, visible light, infrared radiation C. X-rays, gamma-rays, radio waves, visible light D. Visible light, gamma-rays, microwaves, radio waves E. Radio waves, infrared radiation, visible light, x-rays

4 Radiation The intensity of the emitted of radiant energy by a substance is proportional to the fourth power of the temperature (in degrees K). The average frequency of the emitted radiation is proportional to the temperature. A good emitter (and absorber) of radiation is an object whose surface is black. A poor emitter/absorber is an object whose surface is mirror-like or white.

5 The Sun and the Earth The surface of the Sun is at about 6000 K and emits radiation at an average frequency in the visible range of the EM spectrum. The Sun makes its energy by nuclear fusion

6 What type of electromagnetic waves are you (humans) emitting by thermal radiation? A. X-rays B. Radio waves C. Green Visible light D. Infrared radiation E. Ultraviolet light

7 The Sun and the Earth The surface of the Sun is at about 6000 K and emits radiation at an average frequency in the visible range of the EM spectrum. The Sun makes its energy by nuclear fusion The surface of the earth is at about 280 K and emits radiation at an average frequency in the infrared range of the EM spectrum. The earth generates its temperature by nuclear radioactivity in the Earth s interior, and by absorption of radiant energy from the Sun. The Earth captures some of its radiated energy by gas molecules in the atmosphere that absorb infrared light (Greenhouse effect): Greenhouse Gases: CO 2, H 2 O, NH 4, N 2 O

9 Atmospheric Greenhouse Gas Concentration Intergovernmental Panel on Climate Change:

10 Global Temperature minus Average IPCC Intergovernmental Panel on Climate Change:

11 Projected Global Warming IPCC 2001 Intergovernmental Panel on Climate Change:

12 Earth s Atmosphere - Ozone Layer Earth s atmosphere is mostly nitrogen and oxygen. But also has important trace gases such as Ozone that protects us from harmful solar ultraviolet (UV) radiation The middle of the 20 th century saw expanding use of inert molecules called chlorofluorocarbons (CFCs) While CFC molecules are virtually indestructible, they can be broken down in the upper atmosphere by sunlight, releasing chlorine gas, that then reacts with ozone. The depleted ozone would then not able to protect life on Earth

13 Ozone Layer depletion Scientists were able to measure the Ozone layer depletion and confirm that it was attributed to chlorine from CFCs. The 1987 Ozone Treaty was passed limiting the use of CFCs. Industry responded with alternatives, and the Ozone Depletion stopped and reversed.

14 Investment Value Linear Growth Growth by a constant amount per time period $400 $350 $300 $100 Investment Grows by $10 per year $250 $200 $150 $100 $50 $ Year

15 Investment Value Exponential Growth Growth with an unchanging doubling time $1,000 $900 $800 $700 $100 Investment at 10% Growth Rate $600 $500 $400 $300 $200 $100 $ Year

16 Investment Value Exponential Growth is a straight line on a semi-log plot $100 Investment at 10% Growth Rate $1,000 $100 $ Year

17 Doubling Time Doubling time is inversely proportional to the growth rate Doubling Time (T) Growth Rate P Or the percentage growth rate P can be estimated from the doubling time T Growth Rate P 70 T

18 Population growth is exponential 14 Population Density Density People/m 2 Billions 10,000,000 World's Human Population 1,000, ,000 10,000 1, Assumes continued Growth at 1.75% per year Year Assumes continued Growth at 1.75% per year Year It is very unlikely that the population growth rate will be sustainable for even the next century So, what is likely to happen?

19 Sustainable Growth depends on Resources

CHAPTER 2 Energy and Earth

CHAPTER 2 Energy and Earth This chapter is concerned with the nature of energy and how it interacts with Earth. At this stage we are looking at energy in an abstract form though relate it to how it affect