Electromagnetic Radiation, Matter and Energy!

REF: WHO, NOAA, Scientific American

How would our days be different without the sun? Imagine not being able to go outside on a sunny day and bask in the sun's warming rays. Well, don't worry, scientists think that the sun will probably last another 5 billion years, which is a lot longer than Earth will, so we all can breathe easy.

What is the sun made up of? Well, our sun is a ball of tightly packed matter. This matter is under intense pressure due to the sun's gravity. Since this matter is under such intense pressure, the temperature is tremendously high, with a surface temperature = 5,500 C)! The sun's matter, under enormous pressure and temperature, changes state into a highly energetic form of matter called plasma.

In the high temperature and pressure environment of the Sun the plasma gives off packets of energy called photons. Photons have varying amounts of energy, but all move at the speed of light. Thus each photon is a packet, or quanta, of pure energy, moving fast!

Photons given off by the sun with energy levels that an eye can detect are called sunlight. However there are many more types of energy coming from the Sun that a human eye can‚ detect. The general name for ALL different types of energy emitted by the sun is called Electromagnetic Radiation or EMR for short. Electromagnetic Radiation travels amazingly fast, 186,000 miles per second; or 300,000 kilometers per second using the metric system. EMR emitted by the sun reaches the Earth in about 8.3 minutes. Yep, at the speed of light!

Electromagnetic Radiation is pure energy (photons) traveling through space. Thus radiation does not need matter to help it travel through the universe. However, the really interesting thing about Electromagnetic Radiation is that we can see so little of it. All we Earthlings can see is a very, very narrow part of the Electromagnetic Spectrum! That is the part we call light, see figure below.

But as you can now see, that's only part of the story. When one looks at all the different types of EMR plotted together one can see the entire spectrum of EMR. Scientists call this spectrum the Electromagnetic Spectrum. Let‚s learn about these different forms of radiation. (EMR)


The Electromagnetic spectrum lists the most powerful EMR, gamma rays, to the least powerful EMR, radio waves. In addition, the highest energy waves (gamma, x-ray) have the shortest wavelengths. The lowest energy waves, radio waves, have longest wavelengths.

When scientists actually started to look closely at EMR, they discovered that high-energy photons seemed to travel as very tiny waves and also as rays. Lower energy photons seemed to travel as waves. (See figure above) Also, the lowest energy photons travel as really big and long waves, over 3 kilometers long.

Most forms of EMR can be dangerous; however the most dangerous form of Electromagnetic radiation has the most energy. This radiation is called gamma rays. Gamma rays are emitted by the nucleus of an atom and can go through 6 feet of concrete, as well as damage your DNA! Both the sun and nuclear bombs give off gamma rays, as does some tropical lightening.

X-rays, which are emitted by electrons outside of the nucleus, can be less powerful than gamma rays and weak x-rays can go partially through humans. The discoverer of the x-ray, Wilhelm Roentgen in 1896 used his knowledge of EMR to make the first x-ray. Nowadays, x-ray machines have many uses in the medical field.

Another form of EMR, Ultraviolet radiation, can do a lot of long term damage to humans. UV is deadly to most forms of life. Of the three types of Ultraviolet radiation, UVA is most common and has the lowest energy. However, UVA penetrates into the deeper layers of the skin and contributes to skin aging and wrinkling. UVA radiation is also connected to forms of skin cancer.

UVB has the second most energy and cannot penetrate beyond the surface of our skin, but is thought to do a lot of damage to the skin. UVB is responsible for delayed tanning and burning. UVB speeds skin ageing and promotes the development of skin cancer. The atmosphere filters most solar UVB.

UVC rays are the highest energy, and most dangerous type of ultraviolet light. Little attention has been given to UVC rays in the past since they are filtered out by the atmosphere.

Visible light is the next weakest part of the EMR spectrum. All visible light together looks white in color, but when we separate visible light into its parts, we see a rainbow of color! Red light has the largest wavelength and weakest energy, while violet has the smallest wavelength and strongest energy. Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV) are the colors of the rainbow from weakest to strongest energy.

Infrared radiation has a longer wavelength than and possesses less energy than visible light. A home oven uses infrared radiation to cook food and often has infrared (heat) lamps in bathrooms.

Microwave radiation has less energy then infrared radiation. Yet we use microwave ovens to cook food quickly because they cook faster than infrared ovens. Microwaves penetrated deep into food, transmitting energy to the water molecules in the food.This causes these water molecules to vibrate violently and heat the food up rapidly. Infrared radiation doesn't penetrate into food as deeply and so IR cooks food from the outside in, thus cooking with an Infrared (normal oven) takes much longer and uses more energy.

Another very useful form of EMR is Radio waves. Scientists and engineers have worked for years to use this part of the Electromagnetic spectrum to transmit information and music through the air. Thank them for your cell phone!

Light waves are similar in shape to waves in water and sound waves. The names of the different parts of these waves are the same as for any other wave. Check the figure below out!

wave anatomy

The crest is the name for the very top of a wave (A). The trough (B) is the very bottom of the wave. Wave height (C) is the vertical distance from the trough to the crest of a wave. Amplitude is another word for the wave height. The higher the wave height, the more intense the energy is.

The wavelength (D) is the distance measured from crest to crest or trough to trough. The frequency of the wave tells how many waves pass a certain point per second.

Answer all questions in complete, quality & correct sentences reflecting the questions. No pronouns

1. Explain why matter in the sun is in the plasma state of matter?

2. Describe a photon AND tell the different speeds that photons move at.

3. Tell the general name for all types of energy emitted by the sun AND tell how fast these forms of energy move.

4. Use the Electromagnetic Spectrum figure to help you tell the names of all types of EMR in order from high energy to low energy AND tell which has the longest & which has the shortest wavelength.

5. Tell two facts about gamma rays AND tell three sources of gamma rays.

6. Tell two facts about x-rays and also who made the world's first x-ray.

7. Name the most dangerous form of UV radiation and tell which two types of UV humans have to worry the most about.

8. Name the colors of the rainbow from the strongest energy to the weakest energy

9. Explain, if you wanted to cook a potato and save energy, which type of oven you would use And Why you would choose that type of oven?

10. Tell two types radiation not mentioned in 9 above AND explain how humans use these radiations to improve our lives.

11. Draw a figure of a radiation wave and label these parts:

a. trough

b. wave length

c. amplitude

d. wave height

and e. crest

12. EC. Get on the net - search for "the first x-ray‚" & tell what Wilhelm Roentgen made the world's first x-ray of!

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