In this presentation you will:

1. In this presentation you will: Electromagnetic Spectrum Charts • explore the electromagnetic spectrum Next >

2. Introduction Our eyes see only a small band of electromagnetic radiation; the band that we term visible light. There are many other forms of electromagnetic radiation, and collectively they make up the electromagnetic spectrum. All electromagnetic radiation travels through space at the speed of light and through Earth's atmosphere at virtually the same speed. Different forms of electromagnetic radiation differ in their frequency and wavelength. Next >

3. The Electromagnetic Spectrum Chart The following diagram shows a typical electromagnetic (e-m) spectrum chart. Charts of the electromagnetic spectrum are typically used in science for relating wave category, wavelength, and frequency. Next >

4. Radio Waves The electromagnetic waves with the lowest frequency and, therefore, the longest wavelength are known as Radio waves. The relationship between frequency and wavelength is determined by the wave’s velocity in the medium in which it is traveling. Next >

5. Radio Waves Consider a radio wave at 1MHz, traveling in air. The velocity of the wave is approximately equal to the speed of light, 3 × 108 m/s. 1 MHz = 1 × 106 cycles/second 3 × 108 Wavelength = = 300 m 1 × 106 Next >

6. Radio Waves Radio waves are mainly used for communications, including the following applications. • Some broadcast radio and TV transmission • Some person to person radio communication • Model vehicle control The use of the radio spectrum is regulated by governments, who allocate specific bands of frequencies to specific use. Next >

7. Microwaves Microwaves are e-m waves with a wavelength in the range of 1 mm to 1 m (300 MHz – 300 GHz). Some fifty years ago, microwave generation involved bulky equipment and was expensive. Its use was limited to big-budget communications systems, such as radar. Next >

8. Microwaves Today, making use of low-cost microelectronics, microwaves have numerous applications, including the following: • Satellite radio and TV • GPS systems Next >

9. Microwaves • Cell phones • Cooking Microwaves at high levels of power cause liquid molecules to vibrate, creating heat within liquid-based items. This is used to effect in cooking applications, but low-power applications do not create this heating effect. Next >

10. Infrared Radiation (IR) Infrared radiation is the part of the spectrum with frequency immediately below the visible red part of the spectrum. While we cannot see IR, we feel its presence in the form of heat. The heating effect of the Sun is created by the infrared radiation that it emits. Next >

11. Infrared Radiation (IR) Any object that is warmer than the surrounding atmosphere will emit IR. Semiconductor IR emitters and detectors give rise to a number of applications, including the following: • Thermal imaging cameras Next >

12. Infrared Radiation (IR) • Communications – fiber optic cable and wireless controls for multimedia and other equipment • Missile guidance • Fire alarm and intruder alarm systems • Weather forecasting Next >

13. Visible Light Only one form of electromagnetic radiation is visible to the human eye. This range extends from a frequency of 400 THz (red) to 750 THz (violet), approximately. THz represents terahertz.1 THz equals 1012 cycles per second. Next >

14. Visible Light Visible light forms the optical spectrum. There are numerous applications for optics, which include the following: • Cameras • Telescopes • Microscopes • Lasers Next >

15. Ultraviolet (UV) UV light has a wavelength in the range 10 nm to 400 nm. It is named ultraviolet because it is the part of the spectrum with frequencies immediately higher than the violet end of the visible light spectrum. UV light has many uses, including forensics, sterilization, and widespread use in the copying industry. Next >

16. Ultraviolet (UV) While the vast majority of the Sun’s emission is in the infrared and visible ranges, a small amount of the e-m radiation is UV light. Much of the Sun’s UV is blocked by the Earth’s ozone layer, but some reaches the Earth’s surface and creates dangers in exposure to sunlight. It is UV that causes tanning and sunburn. Excessive exposure can result in skin cancer. High levels of UV can also be damaging to eyesight. Next >

17. X-rays X-rays were first observed by a German Scientist, Wilhelm Roentgen, in 1895. Unaware of exactly what they were, Roentgen termed the rays X. These rays have a very short wavelength. Shorter wavelengths of e-m radiation have higher energy levels. Next >

18. X-rays X-rays have sufficient energy to pass through soft tissue and materials, while being absorbed by solid objects. A film placed behind an object subjected to X-ray radiation will show dark ‘shadows’ only where the rays have been absorbed. Next >

19. X-rays X-rays are well known for their use in medical imaging. Image courtesy of Siemens Healthcare From images to identify bone damage to complete body imaging from a CT scanner, X-rays are used extensively in health care. Next >

20. X-rays X-rays are also used in engineering for looking at the structure of materials and for inspection in border and airport security. Exposure to large doses of X-rays is damaging to health. X-rays are emitted from the Sun, but they fortunately do not penetrate the Earth’s atmosphere. An interesting area of Internet research is to investigate how NASA protects astronauts from radiation when they travel in space. Next >

21. Gamma Radiation Gamma radiation is the highest frequency, lowest wavelength e-m radiation. It has the most energy of any form of radiation. Gamma radiation is only produced during nuclear reactions, such as radioactivity, fission, and fusion in stars. Next >

22. Gamma Radiation Gamma radiation is very harmful to living cells. It is used to irradiate food by killing harmful bacteria. In medicine, Gamma radiation treatment is used to kill cancer cells. Next >

23. Question 1 Which of the following statements about an electromagnetic spectrum chart is true? A) The chart only shows exact details for the wavelengths of visible light. B) It shows that as frequency increases, wavelength decreases. C) The chart shows that the energy for any part of the spectrum is the same. D) It shows that as frequency increases, wavelength also increases. Next >

24. Question 1 Which of the following statements about an electromagnetic spectrum chart is true? A) The chart only shows exact details for the wavelengths of visible light. B) It shows that as frequency increases, wavelength decreases. C) The chart shows that the energy for any part of the spectrum is the same. D) It shows that as frequency increases, wavelength also increases. Next >

25. Question 2 Mobile and satellite communication systems typically use which part of the electromagnetic spectrum? A) Radio wave B) Microwave C) Infrared D) Ultraviolet E) X-ray F) Gamma ray Next >

26. Question 2 Mobile and satellite communication systems typically use which part of the electromagnetic spectrum? A) Radio wave B) Microwave C) Infrared D) Ultraviolet E) X-ray F) Gamma ray Next >

27. Question 3 Visible light is only a small part of the electromagnetic spectrum. Approximately what is the wavelength of the visible part of the spectrum? A) 5 m B) 0.5 mm C) 500 nm D) 5 mm Next >

28. Question 3 Visible light is only a small part of the electromagnetic spectrum. Approximately what is the wavelength of the visible part of the spectrum? A) 5 m B) 0.5 mm C) 500 nm D) 5 mm Next >

29. Summary In this presentation you have seen: • the electromagnetic spectrum shown as a chart End >