CHAPTER 7: Waves, Sound, Light

Electromagnetic waves are waves that travel through matter or through empty space. Light waves are composed of two parts – an electric part and a magnetic part.

The intensity of waves is a measure of the amount of energy the waves carry. 2. For light waves, the intensity determines the brightness of the light.

C. The electromagnetic spectrum is the complete range of electromagnetic wave frequencies and wavelengths.

1. Radio Waves 1. Radio waves have wavelengths greater than 0.3 meters. a. they have the longest wavelengths b. carry radio and television signals.

2. Infrared Waves 2. Infrared waves have wavelengths between 0.001 meters and 700 billionths of a meter. - used in remote controls and night vision goggles and emitted by all warm bodies

3. Visible Light 3. Visible light is the range of wavelengths humans can see. It is wavelengths between 700 and 400 billionths of a meter. a. Different wavelengths of light are seen as different colors. b. White light is a combination of all wavelengths of light. c. Violet light has the highest frequency and red light has the lowest frequency.

4. UV radiation 4. Ultraviolet waves have wavelengths between 400 billionths and 10 billionths of a meter -They cause sunburn, and are used for photosynthesis and making vitamin D

5. X-RAYS AND GAMMA RAYS 5. X-rays and gamma rays have the highest energy, highest frequency and shortest wavelength. X-rays are used in medicine to see bones Gamma rays are used in the food industry to destroy bacteria

6. The Sun emits ultraviolet, visible, and infrared waves but most of the UV rays are blocked by Earth’s atmosphere.

D. Sight and The Eye D. You see an object when light waves reflected from the object enter your eye. 1. Light waves enter your eye through the cornea. 2. Light travels to the cornea to the lens which is flexible and helps you focus.

D. Sight and the Eye 3. The focused image is formed on the retina in the back of your eye. 4. Messages from the retina are sent through the optic nerve to the brain so it can process what we see.

5. You see color when light waves of that wavelength are reflected off an object or emitted by the object. 6. The retina contains over 100,000,000 rod and cone cells. a. Rod cells let you see in dim light. b. Cone cells let you see colors.