1. Electromagnetic and Visible Spectrum
Light
Electromagnetic and Visible Spectrum

2. Electromagnetic Waves
Consist of changing magnetic and electric fields moving through space at the speed of light (3.0 x 108 m/s)
Are produced by vibrating charged particles
Do not require a medium

3. Electromagnetic Spectrum
Range of frequencies of electromagnetic waves
As frequency increases, wavelength decreases
As frequency increases, energy of a wave increases

4. Electromagnetic Spectrum
The light we can see is only a small part of all light.
The whole range is called the electromagnetic spectrum and visible light is in the middle of it.
On the low energy end of the spectrum are radio waves. On the high energy end are gamma rays.

5. E-M Spectrum Radio waves Microwaves Infrared Ultraviolet Visible
X-rays
Gamma-rays

8. Radio Waves have the lowest frequency and the longest wavelength.
includes TV waves, which are “vhf” (very high frequency) or “uhf” (ultra high frequency), and radar waves, with highest frequency
Each radio station broadcasts at a set frequency.
Sound waves are converted into electrical signals and change (modulate) the carrier waves.
am - amplitude modulation
fm - frequency modulation
In receiver antennae, electrons are made to vibrate sympathetically at set frequency (concept of resonance)

9. Microwaves Penetrate food evenly.
Match the natural frequencies of large molecules, which vibrate and produce heat to cook food from inside.
Air molecules in the oven are too small to be excited, and microwaves also have no effect on ceramics, plastic, or glass.
Metals reflect microwaves.
Droplets of water absorb microwaves and form steam.
When food is removed from an oven, molecules continue to vibrate, so “stand” time is included in recipes.

10. Infrared Atoms and molecules vibrate to produce infrared waves.
All objects emit infrared waves in the form of heat.
uses for infrared waves:
Sun, fire, radiation, heat lamps used in restaurants

11. Visible Light
electromagnetic radiation to which human eyes are sensitive.
makes up less than 10-6 % of electromagnetic spectrum
different frequencies are seen as colors.
red – lowest frequency and lowest energy
violet – highest frequency and highest energy

12. Ultraviolet Overexposure can cause sunburns and skin cancer
uses: medicine to sterilize surgical instruments by killing bacteria
higher UV frequencies are blocked by gas in atmosphere
Fact or Fiction: Sunlight through a window can give you a sunburn?
Fiction- Ultraviolet rays can not penetrate through a window. It is infrared waves that are passing through and that is why it is warm.

13. X-rays discovered by Wilhelm Roentgen
produced by greatest acceleration of electrons.
uses: x-ray machine for bodies or teeth, to check luggage at airports

14. Gamma Rays highest energy and greatest penetrating power
produced by nuclear reactions, including decay of radioactive atoms and nuclear explosions
kills cancer cells before it kills healthy cells
uses: removing decay-causing bacteria from many foodstuffs or preventing fruit and vegetables from sprouting to maintain freshness and flavor