Bell-Ringer

• 10 February 2009

• Learning Target: Identify the parts of the electromagnetic spectrum and its uses.

• Light is an electromagnetic wave. What evidence have you seen that electricity and magnets are related? Be specific!

WAVES; UNIT 2

Let’s shine some light on it!!

What is the Electromagnetic Spectrum?

The electromagnetic spectrum is the entire range of radiation.

What is radiation?

Radiation is all energy that is released in the form of waves (or rays)

What are some examples of radiation?

1. Gamma Rays

Gamma-ray bursts are the most powerful events in the universe, temporarily outshining several galaxies and likely signaling the birth of a black hole.

What are some uses for radiation?

Gamma Rays are used

• in the sterilization of medical equipment by killing bacteria.

• to kill bacteria and insects in foodstuffs, particularly meat, marshmallows, pies, eggs, and vegetables, to maintain freshness.

What are some examples of radiation?

2. X-Rays

• X-rays can penetrate most materials except lead shielding. When they were discovered, the "X" stood for "unknown," because they were so mysterious. The name has been used ever since.

What are some uses for radiation?

X-Rays are used to…

• examine luggage and in airports for weapons or bombs. (metal detectors use magnetic waves only)

• detect structural problems and cracks in metals that cannot be seen from the outside. (like commercial airplanes and bridges) •most common use of x-rays is in medicine and dentistry

What are some examples of radiation?

3. Ultraviolet Rays

The name means "beyond violet” since violet is the color with the shortest wavelength in the visible light spectrum.

And, UV has even a shorter wavelength than violet! UV rays from a

tanning bed

What are some uses for radiation?

UV rays are used in…

• Security; to help thwart counterfeiters, sensitive documents (like credit cards, driver’s licenses, passports, etc.) may include a UV watermark that can only be seen using a UV-emitting light• Forensics; an investigative tool at the crime scene helpful in locating and identifying bodily fluids (semen, blood, etc.)• Medical; in the treatment of some skin conditions

But wait, there’s more!!And, UV rays are used in…

Nature; some animals, including birds, reptiles, and insects such as bees, can see into the near ultraviolet. • Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision.

• Scorpions glow or take on a yellow to green color under UV illumination thus assisting in the control of these sometimes fatally venomous arachnids.

• Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings.

What are some examples of radiation?

4. Visible Light Rays

The type of radiation that can be detected by human eyes.

It contains the colors of ROYGBIV.

What is colors make up visible light?

Visible Light Rays contain ROYGBIV

• Red• Orange• Yellow• Green• Blue• Indigo• Violet

What are some examples of radiation?

5. Infrared Rays

Medicine: Doctors use infrared to treat skin diseases and relieve the pain of sore muscles. This healing ability sis opposite to the damaging effects of short wavelengths, like X-rays and gamma rays.

Infra means below; Infrared rays have longer wavelengths than visible red light.

They are the barely visible, deep red rays you get from a heat lamp.

What are some uses for radiation?

Infrared rays are used in…

• Science: infrared allows buildings to keep cool even in the summer. Gold transparent films in the windows of large office buildings reflect infrared and help keep temperatures cooler. 

• Photographers use film that is sensitive to infrared rays to take pictures in places where there is no visible light.

• Military uses include night vision goggles, etc.

• And, remote controls, burglar alarms also use infrared. 

What are some examples of radiation?

6. Microwaves

-have wavelengths that can be measured in centimeters!

-The longer microwaves, those closer to 30 cm, are the ones which heat our food in microwave ovens.

-Shorter microwaves are used in remote sensing. These waves are used for radar like doppler, used in weather forecasts.

What are some uses for radiation?

Microwaves are used for…• Communication; Cable, broadband, bluetooth, before fiber optics, most long distance phone calls were sent via microwave.

• Remote sensing; radars use microwaves to detect range and speed of remote objects. Used in doppler radar weather, air traffic control, navigation of ships, and of course, speed limit enforcement.

•Navigation; Global Positioning Systems (GPS) use microwaves

•Food; Microwave ovens produce radiation at exactly the right wavelength to excite water molecules. When water molecules become excited, they heat up. Since most of our food contains a fair amount of water, we can heat up our food by heating up the water inside the food.

What are some examples of radiation?

7. Radio Waves-Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football.

Saturn is a source of intense radio emissions. These are similar to Earth's northern and southern lights.

This is an audio file of radio emissions from Saturn. Radio sounds from Saturn

What are some uses for radiation?

Radio waves are used for…

• detecting explosives such as TNT, an innovation scientists in Japan said could replace X-rays as a more dependable method for screening luggage at airports

• doing more than just bringing music to your radio. They also carry signals for your television and cellular phones.

• Garage door openers, alarm systems, radio controlled toys, and, deep space radio communications.

Electromagnetic Radiation

1. Gamma Rays2. X-rays3. Ultraviolet rays4. Visible light rays5. Infrared rays6. Microwaves7. Radio waves

Let’s summarize…The entire range of radiation includes…

Electromagnetic Radiation

Radio waves have the longest wavelength and the lowest frequency. Gamma rays have the shortest wavelength and the highest frequency.

Electromagnetic Radiation

With visible light… Red has the longest wavelength of all the colors.

 Violet has the shortest wavelength of all the colors.