8.2 Pitch and frequency

• Natuurkunde / Scheikunde
• Middelbare school
• havo, vwo
• Leerjaar 2

8.2 Pitch and frequency

Schedule for this lesson

Explanation the period and frequency of a vibration

Apply knowledge by doing exercises in the workbook

Learning objectives 1/2

-You can write down three factors that affect how high the tone is that a string produces

- You can explain what the frequency of a vibration is

- You can determine the vibration period of a tone in an oscilloscope trace

- You can do calculations using the vibration period and frequency

Learning objectives 2/2

-You can give the frequency range of human hearing

The vibration period and frequency

When a sound is made a vibration is given off

We can see these vibrations in so called oscilloscopes 

The vibration period and frequency

Each square on the oscilloscope gives an amount of time

(1 square is 0,5ms)

And each vibration takes a certain

amount of time to complete

The vibration period and frequency

The vibration period is the amount of time it takes to complete 1 full vibration

In this picture we see multiple vibrations, at which point(s) do we see a completed vibration?

The vibration period and frequency

With the time 1 square takes up, and the amount of completed vibrations we can calculte the vibration period (T)

For example, we have 

3 completed vibrations

What is the time for these 3 vibrations?

The vibration period and frequency

We divide the time it takes to complete a certain amount of vibrations with the amount of vibrations and we get the vibration period (T)

T = 2,4/3=0,8ms = 0,0008

The vibration period and frequency

If we know the period of a vibration we can calculate its frequency (f) in Hertz (Hz)

We can do this with the formula 

f = 1/T

The vibration period and frequency

The frequency means the amount of vibrations that happen over 1 second

For example, if the vibration period is 0,1 s, there are 10 vibrations in 1 s

1/0,1=10

The vibration period and frequency

When we calculated T we got the answer of 0,8ms

Now we can calculate the frequency

f=1/0,0008=1250Hz

Which means 1250 vibrations per second

The vibration period and frequency

Calculate f with a vibration period of...

0,004ms

39ms

and with 0,011

The vibration period and frequency

We humans are able to hear sounds with low and high frequencies

Our hearing range is between 20hz and 20000hz

We can visualize these sounds with a video

Playing a game with the exercises

I have an excel sheet in which i can give points to a team

The amount of point you can get is different each exercise (and is shown on the sheet)

For the rest of the lesson you will make these exercises on a piece of paper, when you are done with 1 exercise you come to me and I will check it

Playing a game with the exercises

When you are correct you will go to the next exercise and you get all points

When you are incorrect you will lose a point, but if you correct the mistake you can still earn a few points. If you are correct after correcting the mistake you will go to the next exercise 

End of the lesson