Doppler Shift Contents: What it is Moving Source Moving observer Whiteboards

Doppler Shift TOC Demo/examples: race cars, bells at RR crossing Frequency: (Key to understanding this) Higher approaching Lower receding Moving source/moving observer

Doppler Shift - moving source TOC Sitting Still

Doppler Shift - moving source TOC Source creates smaller wavelengths in front, longer in back Demo - Doppler appletDoppler applet Moving to the right

Doppler Shift - moving source TOC Derivation: ’ = + u s T f’ = shifted frequency f = source frequency u s = speed of source v = speed of sound When do you use + and - in the denominator?

Doppler Shift - moving observer TOC Motion of the source makes you experience different frequencies Observer

Doppler Shift - moving observer TOC Derivation:f = v/, f’= (v + u o )/ f’ = shifted frequency f = source frequency u o = speed of observer v = speed of sound When do you use + and - ?

Doppler Shift Moving source - approach – f’ Moving source - recede – f’ Moving observer - recede – f’ Moving observer - approach – f’ Moving observer - approach – f Moving source - recede – f Be sure to do at least one of the last two… TOC

290. Hz W A car with a 256 Hz horn approaches you at 40.0 m/s. What frequency do you hear? (3) (use v sound = 343 m/s) Source – approaching f = 256 Hz, u s = 40.0 m/s, v = 343 m/s, and -

973. Hz W A man wearing a pointy hat screams at a perfect Hz while running away from you at 9.5 m/s. What frequency do you hear? (use v sound = 343 m/s) Source – receding f = Hz, u s = 9.5 m/s, v = 343 m/s, and +

81.5. Hz W Your father is nagging you at a pitch of 85.0 Hz, and you ride your motorized “Hello Kitty” skateboard away from him at 14.0 m/s. What frequency do you hear? (use v sound = 343 m/s) Observer, receding f = 85 hz, u o = 14 m/s, v = 343 m/s, and -

Hz W You are running toward the Jo-Jo man with a quarter and a dime at 6.7 m/s. If the music from the truck is at a frequency of 2013 Hz, what is the frequency you hear? (use v sound = 343 m/s) Observer, Approaching f = 2013 hz, u o = 6.7 m/s, v = 343 m/s, and +

426 Hz W Duggan is playing the National Anthem on the electric guitar at the senior assembly. You are late, so you are running toward him at 11.2 m/s. If you hear his last note as an A 440 Hz, what is the real frequency he is making? (use v sound = 343 m/s) Observer, Approaching f’ = 440 hz, u o = 11.2 m/s, v = 343 m/s, and +

562.8 Hz W A group of students wearing pointy hats is riding Ducati motorcycles (The “Hello Kitty” limited edition) and chanting “Respectful, Responsible, Safe” driving away from you at 34 m/s. You hear them at a pitch of 512 Hz, what pitch are they really making? (use v sound = 343 m/s) Source – receding f’ = 512 Hz, u s = 34 m/s, v = 343 m/s, and +

Solving for u s or u o problems (optional)

Moving source lower frequency f’ = f{ v } {v + u s } f’ = 213 Hz, f = 256 Hz, v = 343 m/s, and m/s away from you W What speed in what direction is the same car (f = 256 Hz) moving if you hear 213 Hz (use v sound = 343 m/s)

Moving observer higher frequency f’ = f{v ± u o } { v } f = Hz, f’ = 463 Hz, v = 343 m/s, and m/s W A running person who is late for a concert hears the concertmaster who is playing an A 440. Hz. How fast and in what direction are they running if they hear a frequency of 463 Hz. (use v sound = 343 m/s)

Moving source, then moving observer higher frequency, higher frequency f’ = f{ v } {v + u s } f = 256 hz, u s = 20.0 m/s, v = 343 m/s, and - f’ = f{v ± u o } { v } f = f’ from before, u o = 60.0 m/s, v = 343 m/s, and Hz W You are driving on a road, and a car coming the other way has a horn with a frequency of 256 Hz. The oncoming car is going 20.0 m/s toward you, and you are going 60.0 m/s toward them. What frequency do you hear?