Tuesday, Feb 5, 2008 - 4B

Collected RA 11.2a

Handed back RA 11.1 and went over in class. Students who scored less than 7 could write in correct answers and hand back in.

Introduced the electromagnetic spectrum - all forms of light (transverse waves) that all travel at the same speed through vacuum, 3 x 10^8 m/s or 186,000 miles/sec

Hand out electromagnetic spectrum worksheet.

Radio waves - low frequency, low energy. Transmit in AM and FM. The numbers of the radio stations are the frequencies at which they transmit.
AM 1140 = 1140 kilohertz = 1,140,000 Hz. FM 103 = 103 megahertz = 103,000,000 Hz
Computers and televisions transmit some radio waves which can be picked up on a radio as noise.

Microwaves - need to fit into microwave oven so they have a wavelength of about 30 cm. Used to cook food by jiggling water molecules in food. This jiggling causes heat. Demonstrate cooking Ivory soap and CD in microwave (put cup of water in microwave when doing this)

Infrared - given off by people due to their temperature. Seen by alien in the movie "Predator". Also given off by TV remotes. Demonstrate with photocell and speaker. You can pick up IR signals from the remote on cell phones in camera mode.

Visible light - what we can see with our eyes: ROY G BIV
Red light is lower energy, lower frequency, longer wavelength
Violet light is higher energy, higher frequency, shorter wavelength.

UV - ultraviolet - enough energy to cause sunburn

X-Ray - enough energy to penetrate bodies and give pictures of bones

Gamma Rays - highest energy - given off my nuclei in atoms or by colliding neutron stars.

Handed out flashcard sheets. Students tested each other on vocabulary.

Homework due Wednesday - RA 11.2b Gave students time in class to work on reading assignment homework.

We will have a test on waves on Wed, Feb 13 (I had originally said Monday, Feb 11 but pushed the date back one class)