Thursday, Jan 31, 2008 - 4A

Collected HW - RA 11.1

A vibration is a movement back in forth in time. A wave is a wiggle in both space and time.

Reviewed transverse and longitudinal waves, including wavelength and amplitude, in preparation for the Show Me A Wave Lab. Showed transverse and longitudinal waves with slinky.

Demo with slinky:
High frequency = high energy = short wavelength
Low frequency = low energy = long lazy wavelength

For some waves, including slinky waves, higher amplitude means higher energy.

Belly dancing tuning fork showed sound waves are caused by vibration of tuning fork

Oscilloscope showed that low frequency waves have long wavelength and for sound, low pitch. High frequency sound waves have short wavelengths and for sound high pitch.

Demo with singing rods. Hold in middle to create a node (point of no vibration). Wavelength is twice rod length. Long rod means long wavelength which gives a low pitch sound, low frequency. Short rod means short wavelength which gives a high frequency sound.

Students worked in groups in hallway doing the Show Me a Wave Lab.

Students had 30 min in class to work on homework sheet, RA 11.2b - due next Monday.

Main ideas: transverse vs longitudinal waves
For same wave speed, short wavelength = high frequency which with sound is high pitched. Long wavelength = low frequency which with sound is low frequency.
Students should know what is meant by amplitude, frequency, wavelength.
Sound is a longitudinal wave requiring a medium (matter). Light is transverse and does not require a medium (it can pass through the vacuum of space)