# Electromagnetic Waves the Electromagnetic Spectrum Electromagnetic Waves Transverse

• Slides: 41

Electromagnetic Waves & the Electromagnetic Spectrum

Electromagnetic Waves • Transverse waves without a medium! • (They can travel through empty space)

• EM waves consist of vibrating electrical and magnetic fields that move at the speed of light. – Have some magnetic and some electrical properties to them, and vibrate at right angles to each other. .

Electromagnetic Waves Light and all other electromagnetic waves are produced by charged particles (electrons). Each of these has an electric field around it. This has the ability to push or pull on other charged particles.

When an electric field changes, so does the magnetic field. The changing magnetic field causes the electric field to change. When one field vibrates—so does the other. RESULT-An electromagnetic wave forming electromagnetic radiation.

Electromagnetic waves travel VERY FAST – around 300, 000 kilometres per second (the speed of light). At this speed they can go around the world 8 times in one second. Light from the sun reaches Earth in approximately 8 minutes.

Waves or Particles? • Electromagnetic radiation has properties of waves but also can be thought of as a stream of charged particles (electrons). Each has an electrical field around it. – Example: Light • Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses. • Light as particles-light energy packets (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency RADIO WAVES INFRARED RAYS MICROWAVES ULTRAVIOLET RAYS VISIBLE LIGHT GAMMA RAYS X-RAYS

Electromagnetic Waves The formula that shows how speed, wavelength, and frequency are related. S = W x F

Notice the wavelengths are long (Radio waves) and get shorter (Gamma Rays). Longer the wavelength, less the frequency. Shorter the wavelength, greater the frequency. Greater frequency greater the energy.

RADIO WAVES Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.

Global Positioning Systems (GPS) measure the time it takes a radio wave to travel from several satellites to the receiver, determining the distance to each satellite. https: //www. youtube. com/watch? v=04 VK 5 Xscx. B 4

A radio picks up radio waves (broadcast) through an antenna and converts it to sound waves. – Each radio station in an area broadcasts at a different frequency. • # on radio dial tells frequency.

MRI (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image.

MICROWAVES Have the shortest wavelengths and the highest frequency of the radio waves.

Used in microwave ovens. • Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food.

RADAR (Radio Detection and Ranging) • Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

INFRARED RAYS Infrared= below red Shorter wavelength and higher frequency than microwaves.

You can feel the longest ones as warmth on your skin Warm objects give off more heat energy than cool objects.

Thermogram—a picture that shows regions of different temperatures in the body. Temperatures are calculated by the amount of infrared radiation given off. Therefore people give off infrared rays. Heat lamps give off infrared waves.

VISIBLE LIGHT Shorter wavelength and higher frequency than infrared rays. Electromagnetic waves we can see. Longest wavelength= red light Shortest wavelength= violet (purple) light

Prism can separate the visible light. When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBIV.

ULTRAVIOLET RAYS Shorter wavelength and higher frequency than visible light Carry more energy than visible light

Used to kill bacteria. (Sterilization of equipment)

Small doses of UV rays will stimulate the skin cells to produce vitamin D. The more skin you expose the more vitamin D is produced. Research to date shows that moderate but frequent sun exposure is healthy but overexposure and intense exposure can increase your risk of skin cancer.

Causes your skin to produce vitamin D (good for teeth and bones)

Too much can burn skin, as well as cause skin cancer. Use sun block to protect against (UV rays)

X- RAYS Shorter wavelength and higher frequency than UV-rays Carry a great amount of energy Can penetrate most matter.

Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the xray was absorbed)

Too much exposure can cause cancer (lead vest at dentist protects organs from unnecessary exposure)

Used by engineers to check for tiny cracks in structures. – The rays pass through the cracks and the cracks appear dark on film.

GAMMA RAYS Shorter wavelength and higher frequency than X-rays Carry the greatest amount of energy and penetrate the most.

Used in radiation treatment to kill cancer cells. Can be very harmful if not used correctly.

The Incredible Hulk was the victim of gamma radiation. http: //www. teachertube. com/video/hulk-181049

Exploding nuclear weapons emit gamma rays.

Wave Uses Explain how cellular phones use waves. https: //video. search. yahoo. com/video/play; _ylt=A 2 KLq. ICUMP 1 W 22 s. AOm. Asn. Il. Q; _ylu=X 3 o DMTBz. M 3 Uzbj. Rz. BHNl. Yw. Nzcg. Rzb. Gs. Ddmlk. BHZ 0 a. WQDBGdwb 3 MDMTA? p=how+cell+phone+use+waves&vid=3 bced 5 a 4 d 7919 e 9 cdcc 21 d 19676 a 9 e 70&turl=http%3 A% 2 F%2 Ftse 4. mm. bing. net%2 Fth%3 Fid%3 DOVP. V 7 ce 16 d 6 c 49 e 85 f 1050071136 adb 8981 d%26 pi d%3 D 15. 1%26 h%3 D 166%26 w%3 D 300%26 c%3 D 7%26 rs%3 D 1&rurl=https%3 A%2 F%2 Fwww. y outube. com%2 Fwatch%3 Fv%3 D 0 B 3 lihn. AQog&tit=Cellular+Phones+and+You!+%28 How+does+a

Wave Uses Communications satellites receive radio, TV, and telephone signals and relay those signals back to receivers on Earth.

Wave Uses Explain how GPS works. https: //www. youtube. com/watch? v=04 VK 5 Xscx. B 4

Brief SUMMARY A. All electromagnetic waves travel at the same speed. (300, 000 meters/second) in a vacuum. B. They all have different wavelengths and different frequencies. – Long wavelength- lowest frequency – Short wavelength highest frequency – The higher the frequency the higher the energy.