Calculating wave energy

Waves Benchmark Review

​​If the time is only one second you can count the crests to find the frequency.

​​If the time is given you must use the formula f=waves/time

Multiple Choice

If a wave contains 10 crests in 30 seconds what would the frequency be?

• 3

• 0.33

• 0.25

• 0.67

Multiple Choice

If a wave has 20 crests in 100 seconds. What is the frequency?

• 0.25

• 0.5

• 0.2

• 0.4

Finding the energy

The amount of energy a wave has is calculated by squaring the amplitude (or multiplying the number by itself.

If the wave has an amplitude of 3 then the energy would be 9.

If the wave has an amplitude of 2 then the energy is 4.

For example

Multiple Choice

What is the energy of a wave with an amplitude of 4.

• 8

• 4

• 16

• 12

Multiple Choice

If a wave has an amplitude of 3, then the energy would be

• 9

• 6

• 3

• 12

To calculate the increase in energy

You are going to see problems like this...

Wave a has an amplitude of 2 and wave b has an amplitude of 4. How much more energy does wave b have when compared to wave a.

First we will need calculate each waves energy..

Multiple Choice

If the wave first had an amplitude of 2 what would the energy be?

• 2

• 4

• 6

• 8

Multiple Choice

Then the wave increased to an amplitude of 4. What is the energy now?

• 16

• 6

• 9

• 12

So now we can calculate the difference.

We know wave a was 2 and wave b was 4, the wave's amplitude only increased by 2. Now we could say that the original wave had an energy of 4 and the new wave has an energy of 16.... therefore wave b increased by 4 times because 16/4=4.

Lets see another example.

If the wave has an amplitude of 3 and the next wave has an amplitude of 6 how much more energy does the second wave have.

First we need to calculate the energy of the first wave. 3x3=9 and the second wave 6x6=36. If we see how many times 36 will go into 9 we can find the amount of times the wave increased in energy.

36/9= 4

Multiple Choice

A wave has an amplitude of 3 then increases to an amplitude of 9. What is the energy of each wave?

• wave a= 9

  wave b=10

• wave a= 81

  wave b= 9

• wave a =9

  wave b=81

• wave a = 6

  wave b=18

Multiple Choice

If the wave energy increased from 9 to 81 then the wave has _____ times more energy.

• 3

• 6

• 9

• 12