1. Wave Math
PHYSICS

2. Wave Math
If the scenario doesn’t mention wavelength or frequency then use common sense!

3. Wavelength:
distance between crests λ m

4. Full Wave:
Must have a crest and a trough. C C =
1 ½ waves T

5. Time Period:
seconds
wave
Seconds per wave T s
T = 1 f

6. Frequency:
waves
second
Waves per second f Hz
f = 1 T

7. Velocity: λ meters second T v = λ 1 T Equation 1: v = λ T Equation 2:
v = λf
Notice how the wavelength is directly proportional to the velocity and the time period is inversely proportional to the velocity.

8. Velocity: If the wavelength doubled, the velocity would
_______________.
If the wavelength ¼ the velocity would ___________.
If the time period tripled the velocity would ______.
If the time period ½ the velocity would ___________.
double
1/4
1/3
double

9. Common Sense:
velocity = displacement
time
v = ∆x ∆t

10. Practice Basics
Betty stands on a beach in California counting waves. She counts 15 waves in one minute. She estimates there are 12 meters between waves. Calculate the time period, frequency, and wave velocity.
If the Pacific Ocean is 8,000 kilometers wide, then how much time would it take a wave to cross it?
Could a boat ride the wave across the ocean? Why or why not.

11. Practice With Light
Light travels 300 million m/s. How much time would it take light to circle the Earth once? (Earth radius = 6.37 x m )
Red light has a wavelength of 500 NANOmeters. (There are one billion nanos inside a regular unit.) Calculate the frequency of red light.

12. Practice With Light
When Bob looks at Betty’s dress the cone cells in his eyes detect an electric fluctuation with a frequency of 5.17 x Hz. What color is her dress?

13. Practice With Sound Sound only travels 343 m/s.
Bob sees lightning in the sky (assume light travels so fast he sees it instantly) and then hears the thunder clap 3.5 seconds later. How far away was the lightning?
The note Concert-A that orchestras tune to has a frequency of 440 Hz. Calculate its wavelength.
The lowest sound wavelength that human ears can detect is 17 meters. (METERS!) Long. What is the frequency of this note?