Chapter 4

The Electromagnetic Spectrum

Part 2

Radio waves

• Includes FM, AM, radar and TV waves• Used in many devices such as remote control

items, cell phones, wireless devices, etc.

Microwaves

• First used in radar, now used in communication (wireless LAN networks), and consumer use (microwave ovens).

• medical applications in cancer treatment (destroy tumors by heating them).

• Most radio astronomy uses microwaves

• “Active Denial System” – the “Pain Ray”

Infrared Waves• Infrared radiation is popularly known

as "heat"

• Used in heat lamps, de-icing systems and thermomedic therapy.

• Missile guidance systems, short range communication systems

• Weather satellites

Can be detected with special devices such as night goggles

Weather satellites track weather systems using infrared.

Visible Light

• The portion of the electromagnetic spectrum that human eyes can detect

• ROY G BIV (red, orange, yellow, green, blue, indigo, violet)

• Red is the lowest frequency and violet is the highest frequency

Visible Spectrum

We perceive electromagnetic energy having wavelengths in the range 400-700 nm as visible light.

Ultraviolet

• Can cause skin cancer and blindness in humans

• Used in tanning beds and sterilizing equipment

• UV watermarks• UV identification

Bee vision is very different from human vision, they perceive colors we are simply incapable of seeing. Most insects have light sensitive cells, or photoreceptors, that are sensitive to ultraviolet light.

X-Rays

• Primarily used in medicine.

X-Ray Scanners

X-Ray Diffraction• The diffraction

of X-rays is used to disperse X-rays in a spectrometer and to determine the structure of crystals or molecules.

Gamma rays

• Highest energy and most dangerous type of radiation.

• Can cause cancer through damage to DNA.

• Blocked from Earth’s surface by atmosphere.

• Used in medicine and irradiation.

Irradiation

Gamma Knife

Electromagnetic Waves

Star Finder Video:Electromagnetic Spectrum

Homework

• Chapter 4: Worksheet 2