The Electromagnetic Spectrum

1. The Electromagnetic Spectrum Coach Medford Building Science Champions

2. In Thought • How do you use radio and microwaves in your daily life? Explain in 4-5 sentences.

3. Objectives • Be able to explain and draw the electromagnetic spectrum • Explain how electromagnetic waves differ

4. Key Terms • Electromagnetic spectrum • Radio waves • Microwaves • Infrared waves • Ultraviolet waves • X-ray • Gamma Ray

5. What is the Electromagnetic Spectrum • The changing motion of an electric charge produces each type of electromagnetic wave • Electromagnetic spectrum – entire range of electromagnetic waves that have different frequencies and wavelengths Which waves on the electromagnetic spectrum do you use?

6. Classifying Electromagnetic Waves • The electromagnetic spectrum is organized into different groups based on the wavelengths and frequencies of the waves • Radio waves –have low frequency and low energy, which is low enough that the waves are not harmful • Each wavelength is longer than a kilometer, which is often long enough to move around objects • On Earth, radio waves are usually produced by electric charge moving in an antenna How are radio waves different from each other? What are some of their uses?

7. Microwaves • Microwaves – low frequency and low-energy electromagnetic wave • The wavelength of a microwave is between 1 mm and 30 cm • Microwaves are useful for satellite communication, including cell phones because they can pass through Earth’s upper atmosphere • They are useful for cooking because food molecules absorb their energy Microwaves can be used to broadcast information through space, as well as warm food. They are also used in remote sensing in which microwaves are released and bounced back to collect information on their reflections. Microwaves can be measured in centimeters. They are good for transmitting information because the energy can go through substances such as clouds and light rain. Short microwaves are sometimes used in Doppler radars to predict weather forecasts.

8. Infrared Waves • Infrared waves – wave length shorter than microwaves but longer than visible light • Vibrating molecule in any matter emit infrared waves • You cannot see infrared waves, but you can feel them, such as the warmth of a campfire • Your television remote sends out infrared waves Infrared radiation can be released as heat or thermal energy. It can also be bounced back, which is called near infrared because of its similarities with visible light energy. Infrared Radiation is most commonly used in remote sensing as infrared sensors collect thermal energy, providing us with weather conditions.

9. Visible Light • Your eyes can see visible light • The colors of light range from red, which has the longest wavelength and the lowest frequency, violet which has the shortest wavelength and the highest frequency • Each color name represent a family of colors Visible Light is the only part of the electromagnetic spectrum that humans can see with an unaided eye. This part of the spectrum includes a range of different colors that all represent a particular wavelength. Rainbows are formed in this way; light passes through matter in which it is absorbed or reflected based on its wavelength. Thus, some colors are reflected more than other, leading to the creation of a rainbow.

10. Ultraviolet Waves • Ultraviolet waves – an electromagnetic wave that has a slightly shorter wavelength and higher frequency than light • Carries enough energy to cause a chemical reaction • Earth’s atmosphere prevents most of the Sun’s ultraviolet waves from reaching Earth • Ultraviolet waves have enough energy to penetrate skin and damage or kill cells causing sunburns or even cancer

11. X-Ray • X-Ray – is a high-energy electromagnetic wave that has a slightly higher wavelength and higher frequency than an ultraviolet wave • X-rays have enough energy to pass through skin and muscle but the calcium in the bones stop these rays • Scientist learn about objects in space by studying the X-rays they emit • X-rays are used for medical imaging

12. Gamma Rays • Gamma Ray – high-energy electromagnetic wave with a shorter wavelength and higher frequency than all other types of electromagnetic waves • Gamma rays form when the nucleus of an atom breaks apart or changes • Gamma rays have enough energy to destroy cells • These rays also formed in space during violent events

13. Primary and Pigments of Light • Primary pigment colors of light are: magenta, cyan, and yellow • Black is produced when the three pigment colors blend • Primary colors of light are: red, blue, and green • White is produced when the three primary colors blend

14. To Brain Light waves Light waves How Do We See Colors? Let’s start with our eyes.

15. How Do We See Colors? If there is no light . . . To Brain Light waves Light waves

16. How Do We See Colors? If there is no light . . . To Brain

17. How Do We See Colors? If there is no light . . . To Brain you cannot see because there are no light waves reflecting to your eye. Our eyes only see light reflected off things!

18. How Do We See Colors? The green part absorbs all of the colors except green. It reflectsgreen light. To Brain The red part absorbs all of the colors except red. It reflectsred light.

19. Color Wavelength Red has the longest wavelength Violet has the shortest wavelength

20. Review • A particle of electromagnetic radiation is called a photon • Radio waves are the only electromagnetic waves that do not have a medical use • Microwaves are useful for cooking because food molecules absorb their energy • The number of waves that pass a certain point is one second is the frequency of the wave

21. References • Anderson, M. et all (2012) Physical Science. McGraw-Hill: Columbus • Frank, D.V et al (2001). Physical Science. Prentice Hall: New Jersey • UC Davis – Chemwiki