1 of 10© Boardworks Ltd 2006 Waves 14 May, 2015 Objectives Be able to draw labelled diagrams of waves and describe the 2 sorts of waves. HSW: AF1: Describe

1 of 10 © Boardworks Ltd 2006

Waves

18 April 2023

Objectives

Be able to draw labelled diagrams of waves and describe the 2 sorts of waves.

HSW: AF1: Describe and explain processes logically and in detail, making use of abstract ideas and models from different areas of science.

Used before in: Will use again in:

PLTS: Independent enquirers: support conclusions, using reasoned arguments and evidence.

Used before in: Will use again in:

KeywordsWavelength, amplitude, frequency, Hertz, speed, transverse,

peak, trough, longitudinal, compression, rarefaction.


Outcomes

All students should be able to: • Describe what a wave is.Most students should be able to: • Draw labelled diagrams that show the

wavelength, amplitude, peak and trough and be able to define the frequency and speed of a wave.

• Be able to describe the properties of transverse and longitudinal waves.

Some students should be able to: • Use models to explain the differences between

transverse and longitudinal waves.


What is a wave?

A wave is a series of disturbances that are the same distance from each other and transfer energyfrom one place to another. There are 2 types of wave:

Transverse

Longitudinal

Task: Copy the slide and then come over to watch the demo of a slinky


STUDENT MODELLING

• We have seen how we can model waves with a slinky;

• We can also model waves with students.• What does each student represent?• Could you explain the differences between

transverse and longitudinal waves using this model?

• What type of wave is sound? – How could you use this model to show how sound travels at different speeds through solids, liquids and gases?


A Slinky can be used to model transverse waves, by moving one end of the Slinky up and down.

What do transverse waves look like?

The wave travels away from the source. The direction of the wave is at right angles to the movement of the source.

source movesup and down

direction of wave

coils vibrateup and down

In a transverse wave, the coils do not travel horizontally, each coil of the Slinky just vibrates up and down.


Simulation of a transverse wave


Water waves and electromagnetic waves, such as light, are examples of transverse waves.

Certain parts of a transverse wave have special names.

What are the parts of a transverse wave?

peak

troughwavelength

wavelength

wavelength

The wavelength is the same whichever two matching points are used to measure this distance. The symbol used to represent wavelength is .

amplitude

amplitude

The amplitude of any wave is the maximum distance a point moves from its rest position.


Investigating transverse waves


What do longitudinal waves look like?

A Slinky can be used to model longitudinal waves, by moving one end of the Slinky left and right.

The wave travels away from the source. The direction of the wave is parallel to the movement of the source.

source movesleft and right

coils vibrateleft and right

direction of wave

In a longitudinal wave, the coils do not travel horizontally, each coil of the Slinky just vibrates left and right.


Simulation of a longitudinal wave


Certain parts of a longitudinal wave have special names.

compression

rarefaction

What are the parts of a longitudinal wave?

Sound waves are longitudinal waves. When someone speaks, the air particles vibrate as a longitudinal wave and so compressions and rarefactions are formed in the air.

Sections that are pushed together are called compressions and that are stretched out are called rarefactions.

wavelength

wavelength


The frequency is the number of waves passing any point each second.

frequency = number of waves past a point / time

frequency is measured in hertz (Hz)

1 wave per second = 1 Hz

If this set of transverse waves pass a point in one second, what is the frequency? 4 Hz

Frequency of transverse waves


PRACTICAL TIME!! – 1st finish the diagrams below:

• 2nd – Get a worksheet, ruler and goggles and do the answers to the worksheet in your exercise book. Do NOT write on the sheets please.

compression

rarefaction

wavelength

peak

troughwavelength

wavelength

wavelength amplitude

amplitude

wavelength


PRACTICAL TIME – The BIG Q: How can we describe what waves are?

Procedure and Questions1. Place the ruler on the table so that half of it hangs over the edge.2. Hold the ruler firmly against the table, and twang the end of the ruler.

Listen to the sound it makes.3. If more of the ruler were hanging over the edge of the table when you

twanged it, how do you think the sound would be different? Why?4. Test your answer to number 3. Describe what happened.5. If less of the ruler were hanging over the edge of the table, how do

you think the sound would be different? Why?6. Test your answer to number 5. Describe what happened.7. Draw pictures of the three positions of the ruler.

Then, draw arrows or other symbols to show how the sound changed in each case. Finally, use the names of the properties of waves to label your diagrams and help describe what happened during this activity.

Properties• Longitudinal• Amplitude• Wavelength• Frequency

In your description: ALL should describe what a wave is.MOST should draw a labelled diagram of the type of waves coming off describing how they are different.SOME should explain how you could model these waves in some other way.


Transverse or longitudinal waves?


Frequency of waves – activity


Wavelength Hertz crest

period amplitude longitudinal

trough transverse sound

Documents

1 of 10© Boardworks Ltd 2006 Waves 14 May, 2015 Objectives Be able to draw labelled diagrams of waves and describe the 2 sorts of waves. HSW: AF1: Describe