SOCES ExplanaJam 2025 Winners

ExplanaJam 2025 The Doppler Effect

Henry G. and Bruno Z. earned 1st place HS category in CSUN's Science ExplanaJam 2025 with their 3 minute video explaining the phenomenon of "The Doppler Effect" ! CSUN's Science Learning Collaboratory (CSLC) scored over 140 videos based on submissions from 53 classes (over 700 videos total were created for this contest).

ExplanaJam 2025 The Doppler Effect

Show Transcript

hello all today I will be showing you all something very interesting you see you guys heard that too right how is it that his voice went from a higher to a lower pitch well believe it or not is phenomenon is caused by something called the Doppler effect so sound and light travel as waves which are interpreted by Asen machines based on their amplitude or height and frequency which is the amount of times a wave passes by a point every second oh okay I so if 1 of these waves of moving with a velocity relative to a person then the number of wave Cycles interpreted per second by that person would change which then changes the waves frequency and when you change a sound waves frequency it Alters the pitch which is why the pitch of my voice changed when I ran by you with a velocity exactly that's what the Doppler effect is okay okay this sounds right but how would we prove it well let me show you here we've set up an experiment where we're going to be seeing the Doppler effect in action we're going to be using this microphone in order to capture sound waves emitted from my car passing by momentarily in addition we have a microphone stationed inside the car in order to compare the pitches that are captured by both microphones let's begin hi uh let's run that back in slow-mo all right so as we can see the car is moving towards the center of my phone at this current moment with a positive velocity this means that the waves that the car the sound is the car is emitting are also traveling towards the center microphone with a positive velocity this means that they hit the center microphone faster therefore decreasing their cycle time increasing their frequency increasing their pitch as we can see with the pitch of the center microphone uh picking up a higher pitch than our control which is inside the car and has no relative velocity to the car now is the car moves towards the center microphone and becomes equal is it the pitches of our control in the center microphone actually equalize uh this is because the current sound waves car our meeting that are hitting this on our microphone are traveling this way which means our frequency doesn't change with the velocity or speed given to them by the car moving this way and this way because they're traveling this way now of course this changes is the car moves away from the center microphone and starts traveling towards that direction uh because the sound waves are actually slowing down by the velocity given to them by the car which means that they hit the center microphone with an increased cycle time therefore a decreased frequency and a decreased pitch as you can see with the pitch of the center microphone being lower than our control all right let's wrap this up and head back to the classroom wow the Doppler effect is super interesting yeah in fact the Doppler effect works on all waves when we look super far out into Universe at the starts at planets moving away from us really really fast we find that the light waves they emit actually shift in frequency making them look a little bit more red than usual scientists call this red shift but that's a topic for a whole other 3 minute video thanks for watching