Science 10 Mr. Jean April 12 th, 2012

The plan: Video clip of the day Sonic Booms Properties of sounds & light Radar Guns Doppler Effect

θ Sonic boom manifested by condensation of water in air Sonic Boom: sin  = v sound /v source = 1/“Mach number”

Sonic boom of bullet in flight (holographic interferometry?) Sonic Boom: How fast is the bullet traveling? –Mach # = 1/sin 

Super Sonic Flight: ng_resources/boom_script_f lash.htmlhttp://stokes.byu.edu/teachi ng_resources/boom_script_f lash.html

What is Sound? Audacity demonstrations –Typical Sound –Sound waves –Interference –Demonstration of Wave Superposition

Visible Spectrum:

DOPPLER EFFECT Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves n Doppler Movie - URL URL

When a source of waves and an observer of waves are getting closer together, the observer of the waves “sees” a frequency for the waves that is higher than the emitted frequency. When a source of waves and an observer of waves are getting farther apart, the observer of the waves “sees” a frequency for the waves that is lower than the emitted frequency.

n All waves exhibit the Doppler effect. A particularly interesting example is used by astronomers to determine if light emitting objects (such as stars) are getting closer to us or farther away. On average most stars are moving farther away, and their light spectra are “red shifted.”

Red Shift: Moving Away from source Actual Visual Spectrum Observed Visual Spectrum

Blue Shift: Moving towards source Actual Visual Spectrum Observed Visual Spectrum

n Radar bounced off a spinning planet can exhibit a Doppler effect and lead to a determination of the spin rate of the planet. This was used to discover that Venus has a retrograde spin. Of course police use the Doppler effect to catch speeding motorists.

Doppler Effect: doppler_script_flash.htmlhttp://stokes.byu.edu/teaching_resources/ doppler_script_flash.html Doppler Experiment Demonstration

Radar Guns: