Monday, Feb 9, 2009 - Block 4B

Sent a student out of the room and around the corner. Asked if they could hear me? see me? The sound waves bend around the corners so you can hear around corners. The light bends a little too, but it has a short wavelength so it does not bend as much.

Diffraction - the bending of a wave around a barrier or through an opening. The longer the wavelength, the greater the bending. Sound waves have a much longer wavelength than light so sound bends more. You can hear around corners but not see around corners due to diffraction.

Put a pencil in a cup of water. It appeared to be bent. This was due to refraction.
Refraction - the bending of a wave as it goes from one material into another.

Brought out a mirror - what do you see in it? A reflection. Light waves bounce off the surface of the mirror. Held it up so one person could see the image of another. I then moved the mirror to the side and the first person could no longer see the image of the second. The angle of the incoming wave (incident wave) is equal to the angle of the outgoing (reflected) wave.

Showed belly-dancing tuning fork with computer. Waves are caused by vibrations. Waves are wiggles that move through space. If you look closely you can also see nodes and antinodes.

Went over RA 11.1
Handed out RA 11.2a, RA 11.2b and allowed students to get books and work on the reading assignments in class.