17.2 Waves of the electromagnetic Spectrum

1. 17.2 Waves of the electromagnetic Spectrum Pg. 578 - 585

2. What is the Electromagnetic Spectrum? • All electromagnetic waves travel at the same speed in a vacuum, BUT they have different wavelengths at different frequencies • Visible Light: Is radiation in the wavelengths that your eyes can see • Only a small portion of electromagnetic radiation is visible light • The rest of the wavelengths are invisible

3. Visible Light

4. What is the Electromagnetic Spectrum? • Recall how speed, wavelength, and frequency are related • Speed = Wavelength X Frequency • As the wavelength decreases, the frequency increases • Waves with the longest wavelength have the lowest frequencies • Waves with the shortest wavelength have the highest frequencies • **The higher the frequency, the higher its energy

5. What is the Electromagnetic Spectrum? • The Electromagnetic Spectrum is the complete range electromagnetic waves placed in order of increasing frequency • The Order: • Radio Waves, Infrared Rays, Visible Light, Ultraviolet Light, X-rays, and Gamma Rays

6. Radio Waves • Radio Waves are the electromagnetic waves with the longest wavelengths and lowest frequencies • There are two types of Radio Waves: • 1. Broadcast Waves (Radio and TV) • 2. Microwaves

7. Broadcast Waves • Radio waves with longer wavelengths are used in broadcasting • They carry signals for both radio and television programs

8. How Broadcast Waves Work • A broadcast station sends out radio waves at certain frequencies • A radio or TV antenna picks up the waves and converts the radio signals into electrical signals • Inside radios the electrical signals are converted into sound • Inside TVs the signal is converted into sounds and pictures

9. Microwaves • Microwaves are radio waves with the shortest wavelengths and highest frequencies. • Microwaves have many uses • Cellular phones, cooking, and radar

10. Radar • Radar stands for Radio Detection And Ranging • Radar is a system that uses reflected radio waves to detect objects and measure their distance and speed

11. Radar • To measure distance: • A radar device sends out radio waves that reflect off an object • The time it takes for the reflected waves to return is used to calculate the object’s distance • To measure speed: • A radar device uses the Doppler effect • The difference in frequency is used to calculate the car’s speed

12. Infrared Rays • Infrared Rays are electromagnetic waves with wavelengths shorter than those of radio waves

13. Heat Lamps • Infrared rays have more energy than radio waves • You feel the energy of infrared rays as heat • Heat lamps have bulbs that give off mostly infrared rays and very little visible light • Heat lamps are used to keep food warm or heat up rooms quickly

14. Infrared Cameras • Most objects give off some infrared rays • Warmer objects give off infrared rays with more energy and higher frequencies • Infrared cameras take pictures using infrared rays instead of light • These pictures are called thermograms, which is an image that shows regions of different temperatures in different colors • Used by firefighters to locate people during fires

15. Visible Light • Visible light are electromagnetic waves that we can see • Visible light has shorter wavelengths and higher frequencies than infrared rays • Visible light with the longest wavelength appear red • Visible light with the shortest wavelength appear violet in color

17. Ultraviolet Rays • Ultraviolet Rays are electromagnetic waves with wavelengths shorter than those of visible light • Ultraviolet Rays have higher frequencies than visible light so they have more energy • Have enough energy to damage or kill living cells • Ultraviolet lamps are used to kill bacteria on hospital equipment

18. Ultraviolet Rays and Health • Small doses of ultraviolet rays are useful! • Cause skin to produce vitamin D, which is needed for healthy bones and teeth • Large doses of ultraviolet rays can be harmful! • Can burn your skin, which causes skin cancer and damage to your eyes • By applying sun block and wearing sunglasses you can limit the damage caused by ultraviolet rays

20. X-Rays • X-Rays are electromagnetic waves with wavelengths just shorter than those of ultraviolet rays • X-Rays have higher frequencies than ultraviolet rays = more energy • X-Rays have so much energy they can penetrate most matter except bone • Bones absorb X-rays

21. How X-Rays Work • Bones absorb X-rays and does not allow them to pass through • X-rays pass through skin and soft tissue, causing the photographic film in the X-ray machine to darken when it is developed • Bones absorb the X-rays and appear as the lighter areas on the film

22. X-Rays • Too much X-ray exposure can cause cancer • When X-rays are taken a lead apron is worn during the procedure • The lead apron absorbs the X-rays and prevents them from reaching your body

23. Uses of X-Rays • X-rays are sometimes used in industry and engineering • Used to find out if steel has any tiny cracks because the X-rays will pass through the tiny cracks that are not visible to the human eye • Used to check the quality of joints in oil and gas pipelines

24. Gamma Rays • Gamma Rays are electromagnetic waves with the shortest wavelengths and highest frequencies • Gamma Rays have the most energy • Are the most penetrating of all of the electromagnetic waves

25. Uses of Gamma Rays • Radioactive substances and nuclear reactions produce gamma rays • Gamma rays are also used in medicine • Used to kill cancer cells inside the body • Used to examine internal body structures • A patient will be injected with fluid that emits gamma rays • The gamma ray detector can form an image of the inside of the body

26. Gamma Rays and Space • Some objects in space give off bursts of gamma rays • Gamma Rays are blocked by Earth’s atmosphere • Gamma ray telescopes that detect the gamma rays must orbit above the Earth’s atmosphere • Astronomers believe that explosions of stars in the distant galaxies are one way of producing gamma rays