1. 24.3 The Sun Structure of the Sun
Because the sun is made of gas, no sharp boundaries exist between its various layers.
Keeping this in mind, we can divide the sun into four parts: the solar interior; the visible surface, or photosphere; and two atmospheric layers, the chromosphere and corona.

2. 24.3 The Sun
 Photosphere
• The photosphere is the region of the sun that radiates energy to space, or the visible surface of the sun.
• It exhibits a grainy texture made up of many small, bright markings, called granules, produced by convection.
• Its temperature averages approximately 6000 K (10,000ºF).

3. Structure of the Sun
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4. 24.3 The Sun
 Chromosphere
• The chromosphere is the first layer of the solar atmosphere found directly above the photosphere.
• It is a relatively thin, hot layer of incandescent gases a few thousand kilometers thick.
• Its top contains numerous spicules, which are narrow jets of rising material.

5. Chromosphere
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6. 24.3 The Sun
 Corona
• The corona is the outer, weak layer of the solar atmosphere.
• The temperature at the top of the corona exceeds 1 million K.
• Solar wind is a stream of protons and electrons ejected at high speeds from the solar corona.

7. 24.3 The Sun
• A sunspot is a dark spot on the sun that is cool in contrast to the surrounding photosphere.
• Sunspots appear dark because of their temperature, which is about 1500 K less than that of the surrounding solar surface.

8. Sunspots
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9. 24.3 The Sun
• Solar flares are brief outbursts that normally last about an hour and appear as a sudden brightening of the region above a sunspot cluster
• Solar flares release large amounts of energy, much of it in the form of ultraviolet, radio, and X-ray radiation
• Auroras, the result of solar flares, are bright displays of light caused by solar radiation interacting with the upper atmosphere at our poles

10. Aurora Borealis
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11. 24.3 The Sun • Nuclear fusion is the way that the sun produces energy.
This reaction converts four hydrogen nuclei into the nucleus of a helium atom.
 Heat is the energy transferred from one object to another because of a difference in the objects’ temperature.

12. 17.2 Heating the Atmosphere
Energy Transfer as Heat
17.2 Heating the Atmosphere
 Three methods of energy transfer as heat are conduction, convection, and radiation.
 Conduction is the transfer of heat through matter by molecular activity.
 Convection is the transfer of heat by mass movement or circulation within a substance.

13. Energy Transfer as Heat
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14. Sunlight Reaching the Earth
Light from the Sun reaches the Earth through the process of radiation
Two layers are protecting us from radiation:
A) Ozone Layer  Blocks out many forms of radiation that travel from various locations in space
B) Electromagnetic Field (EM) Is an invisible shield made from the spinning of Earth’s outer core
protects even more than the ozone layer

15. 24.1 The Study of Light
 Electromagnetic radiation includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves.
 The electromagnetic spectrum is the arrangement of electromagnetic radiation according to wavelength.

16. Electromagnetic Spectrum
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17. Electromagnetic Spectrum
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18. Types of Radiation 1. Gamma Radiation
Source of Radiation Cosmic rays from dying stars
Uses  Radiotherapy for cancer treatments and the irradication of bacteria and other organisms
Effects on Humans In small doses, gamma rays will pass right through our bodies
In high doses, gamma rays can lead to cell damage and mutations

19. Radiation (con’t) 2. Visible Light
Source of Radiation Anything that produces light
Uses The eye interprets light (colors)
Also used to read and transmit information from DVD’s and CD’s
Effects on Humans No true bad effects, but if you stare at the Sun for long periods of time, it could cause eye damage

20. Radiation (con’t) 3. Ultraviolet Radiation Sources of Radiation SUN
Uses  Tanning of skin
 Detecting forgeries in documents and money
 Sterilization of products that come in contact with bacteria and unclean conditions
Effects on Humans
Sunburns when exposed for long periods of time, and if you are repeatedly sun burned, then it can lead to skin cancer

21. Radiation (con’t) 4. Microwaves
Source of Radiation Magnetic fields from stars and large amounts of heat that is given off from space bodies
Uses Cooking of food at high temperatures in short periods of time
Newer cell phones
Radar found in the military and airports
Effects on Humans  Nervous system cancers
Cataracts in eyes slowly destroy your vision
If exposure is prolonged it can lead to permanent brain damage or cancer

22. Radiation (con’t) 5. Radio waves
Sources of Radiation Magnetic fields from stars and large amounts of heat given off from space bodies
Uses  Communications
Effects on Humans  Nervous system forms of cancer and leukemia

23. Radiation (cont.) 6. X-Rays
Source of Radiation Cosmic Rays from dying stars
Uses Medical bio scans and bomb detection
Effects on Humans  bone cancer if not protected
Takes high levels exposure for effects to happen

24. 17.2 Heating the Atmosphere
 Electromagnetic Waves
• The sun emits light and heat as well as the ultraviolet rays that cause a suntan.
These forms of energy are only part of a large array of energy emitted by the sun, called the electromagnetic spectrum.

25. 17.2 Heating the Atmosphere
Energy Transfer as Heat
17.2 Heating the Atmosphere
• Radiation is the transfer of energy (heat) through space by electromagnetic waves that travel out in all directions.
• Unlike conduction and convection, which need material to travel through, radiant energy can travel through the vacuum of space.
• All objects, at any temperature, emit radiant energy.

26. 17.2 Heating the Atmosphere
What Happens to Solar Radiation?
17.2 Heating the Atmosphere
 When radiation strikes an object, there usually are three different results.
1. Some energy is absorbed by the object.
2. Substances, such as water and air, are transparent to certain wavelengths of radiation.
3. Some radiation may bounce off the object without being absorbed or transmitted.

27. Solar Radiation
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28. 17.2 Heating the Atmosphere
What Happens to Solar Radiation?
17.2 Heating the Atmosphere
 Absorption
• About 50% of the solar energy that strikes the top of the atmosphere reaches Earth’s surface and is absorbed.
• The greenhouse effect is the heating of Earth’s surface and atmosphere from solar radiation being absorbed and emitted by the atmosphere, mainly by water vapor and carbon dioxide.

29. What Happens to Solar Radiation?
In the process of photosynthesis, plants convert radiant energy from the sun into chemical energy in the form of glucose (sugar)

30. 17.3 Temperature Controls Why Temperatures Vary
• Land heats more rapidly and to higher temperatures than water. Land also cools more rapidly and to lower temperatures than water.