more obvious for radio waves
- more obvious for radio waves
- AM radio f = 1 MHz, ? = speed/f = 300 m
- FM radio f = 100 MHz, ? = 3 m
- FM “T-shaped” antenna tuned to 1/4 wavelength
-
Demonstration with sound waves
- pendulum or spring, period 1-2 s, creates sound wave, can’t hear it
- ear insensitive below 20 Hz
- ~ 400 Hz tuning fork
- made much louder by coupling to box
- wood in box can move much more air than tines of tuning fork
- Ear has very poor image resolution
- close eyes and move across room with tuning fork -- very hard to locate