The Doppler Effect
The Doppler Effect
Have you ever heard the tell-tale sound
Of a distant ice cream truck,
And you run outside with your crumpled bills
As you thank your precious luck?
You can hear that one familiar tune
That you’ve heard so many times,
And you know the truck’s approaching you,
For the pitch is bending high.
You take your prize with the gumball eyes
While the driver turns to go;
As he drives away the song acquires
A slightly eerie tone.
For the farther and farther down the road
The truck so quickly goes,
The lower and lower and lower than low
The song’s pitch seems to go.
What is the cause of this warping sound,
The truck’s lamenting moan?
What grief resides in its bending howl?
What is its hidden woe?
Does it wish to be a taco truck?
Is it tired from its load?
Does it curse its fate forever stuck
On a long, monotonous road?
Well, the truth of it is much profound,
But it’s not what you’d expect;
This bending pitch and warping sound
Is called the Doppler effect!
The ice cream truck approaches you
While on the curb you wait;
Meanwhile its fun and quirky tune
Ripples towards you in waves.
The moving truck gives every wave
A helpful, forward push;
Each wave has a shorter path to take,
So they reach you squashed and smooshed.
And as the waves compress, the frequency
Appears to rise,
And frequency is pitch, you see,
So the pitch appears to climb.
And the opposite of this is true:
As the truck rumbles away,
Each wave takes longer to get to you,
So the pitch bends down and fades…
This effect that Mr. Doppler found
Works for any kind of wave;
Radio, water, light, or sound,
It happens all the same.
Essentially, this Doppler Effect
Is a trusty speed radar;
Police even use it to detect
The speed of motor cars.
It’s also used in medicine
For measuring blood flow;
It can uncover evidence
Of heart defects unknown.
But even crazier is its use
In the field of astronomy;
It helps astronomers deduce
The movement of galaxies.
It’s been well used to supplement
And enrich our understanding;
According to the Doppler effect
The universe is expanding!