Lesson Plan 22 – Making Waves

Lesson Plan 22 – Making Waves |

© 2011 | ABC Science Online

Lesson Plan 22

Making Waves

In deep water,* every water molecule moves in a circular orbit and returns to its

starting position as a wave passes by. In this activity, students build a simple

computer model of a water molecule’s orbital motion using standard presentation

software.† They copy, paste and animate their model to discover the motion of

individual water molecules hidden within every wave.

Students can share their animations by converting the presentation to a movie

format that can be uploaded to the school website, social networks or YouTube.

This lesson plan should be used in conjunction with the instructional video of how

to build the wave animation in the lesson plans section of the Surfing Scientist

website at: abc.net.au/science/surfingscientist/lessons

* Deep-water waves are waves travelling in water deeper than half the wavelength of the wave. (See

introduction to waves on page 3.) † This animation can be created with Microsoft PowerPoint (PC) or Apple Keynote (Mac).

Duration: 45–60 minutes

Year Level: Middle to upper primary, secondary

Topics: Energy, motion, water waves, computer skills, multiplication and

division, circles, geometry

Preparation: 5–15 minutes

Overview

Whole class Introduce and discuss lesson on SMART BOARD.

Individual Students design, format and test the behaviour of their molecules.

Next, they copy, paste, align and animate to create their wave

model.

Whole class Optional: students present their wave model on the SMART BOARD

or projector.

Materials

• Requires either Microsoft PowerPoint or Apple Keynote software.

• Student worksheet.

Preparation Photocopy worksheets and introduction to water waves (4 to 6). Try building the

animated model yourself so that you can foresee problems and assist if students

have difficulties.



Objectives

Science concepts

In ‘deep water’, the water molecules in a wave move in circular

orbits.

The distance between two wave peaks is called the wavelength.

The time it takes two wave peaks to pass a stationary point is called

the wave period.

Waves moving in water deeper than half the wavelength of the

wave are called deep-water waves.

Waves moving in water shallower than one-twentieth of the

wavelength of the wave are called shallow-water waves.

Deep-water waves do not reach or interact with the sea floor.

Shallow-water waves interact with the sea floor.

The molecules in shallow-water waves move in elliptical orbits that

become flat at the sea floor.

Numeracy skills

Calculate the number of increments.

Calculate the angle to set each molecule.

Computer skills

Draw, format and align objects.

Copy, paste and animate drawing objects.

Procedure

Discuss the lesson

Discuss ocean waves and demonstrate your animated wave model on the

SMART BOARD or play the wave animation online video. Discuss how to draw,

format, copy, paste and animate the objects.

Students use computers to create wave animation

Distribute worksheets and assist students.

Optional class presentation

Students copy their presentation to a USB memory device and load onto the

SMART BOARD to present the animation to the whole class.



Teacher Notes

These notes are further to the student worksheet

STEP 1 – Draw a molecule

The basic unit only needs to be drawn once. It consists of two

circles grouped together so the smaller circle (‘molecule’) rotates

around the centre of the larger circle (‘orbit’). An additional circle

in the centre and a vertical line can be added to make the

rotation around the circular orbit clearly visible during the

animation. Any resizing may require reformatting of line

thicknesses, followed by realignment.

STEP 2 – Copy, paste, align and preset angles

Once the basic unit has been drawn, copy and paste so that nine orbits fit side by

side across the slide. The remaining 16 molecules are distributed evenly between

Molecules 1 and 9. (See hint* below.)

The preset angle of 15° between molecules is calculated by dividing a full rotation

(360°) by 24. Note that there are 25 molecules but molecules 1 and 25 start in the

same orientation, hence divide 360° by 24 (not 25). To preset:

PowerPoint: Format Shape > Size > enter angle in ‘Rotation’ setting.

Keynote: Select Inspector > Metrics > entre angle in ‘Rotate’ setting.

Nine aligned side-by-side

25 distributed evenly*

Preset angles

* HINT: distributing the 25 molecules evenly may require drawing 25 vertical lines to use as a guide against which

to align the molecules by hand (using the mouse or the left and right arrows on the keyboard).

STEP 3 – Animate molecules to create wave

PowerPoint: Select ‘Add effect’, then ‘Emphasis Effect’ and choose ‘Spin’. Then set these options: Start

‘With Previous’, Property ‘Two Spins’ (720° Add), Speed ‘Very Slow’. In ‘More Effect Options’ uncheck

‘Smooth Start’ and ‘Smooth End’.

Keynote: Select ‘Inspector’, then ‘Build’ (diamond icon) and choose ‘Action’. Then set these options:

Effect ‘Rotate’, Direction ‘Clockwise’, Rotate ‘720°’, Acceleration ‘None’, Duration ‘5 seconds’ (or more).



Introduction to waves The waves you see rolling in at the beach are called surface gravity waves. They are generated by wind blowing over the ocean. The stronger the wind and the longer it blows, the bigger the waves become. The distance over which the wind that forms waves blows is called the fetch. After the wind stops, gravity’s pull keeps waves moving until they reach a shoreline and break, or spread out so much that they are imperceptible. The distance between two wave peaks is called the wavelength. The time it takes for two peaks to pass a stationary point is called the period. Waves look like big lumps of water moving across the ocean but this is an illusion. The individual water molecules move in circular orbits and return to their starting position so that there is almost no net displacement of water. Waves behave differently in ‘deep’ and ‘shallow’ water. The diagrams below illustrate what scientists mean by ‘deep’ and ‘shallow’ water when describing the behaviour of waves.

NOTE: In real waves, the orbits (in red) of both deep and shallow water waves are not perfectly closed and there is a small displacement of water called ‘Stokes drift’.

Deep-water waves When the water is deeper than half the wavelength, the waves are called deep-water waves. Here, the water molecules move in circular orbits that become smaller with depth. Below a depth equal to half the wavelength of the wave, the water doesn’t move at all. A scuba diver below this depth won’t feel the waves above. That’s why they are called ‘surface’ gravity waves (i.e., they don’t extend all the way to the sea floor). The speed of deep-water waves is around 60 to 100 kilometres per hour and depends only on their wavelength. The longer the wavelength (i.e., the distance between peaks) the faster the wave. Shallow-water waves When a wave enters water that is shallower than one-twentieth of the wavelength (i.e., the wavelength divided by 20), it becomes a shallow-water wave. The circular motion becomes flattened into elliptical orbits. At the sea floor, the water molecules can only move back and forth (not up and down). Friction between them and the sea floor causes the wave to slow down. In shallow water, a wave’s speed depends only on the depth of the water. The shallower the water the slower the wave’s speed. Breaking waves and surfing At depths between one-half (deep water) and one-twentieth of the wavelength (shallow water), the waves are called transitional waves. As they move from deep water into shallow water, waves slow down. If the sea floor is the right shape, they can slow down so rapidly that the top topples over and breaks towards the shore. This is the point at which surfers can catch and ride waves.



Wave animation instructions

This animation works with Microsoft PowerPoint (PC) or Apple Keynote (Mac). It models the circular orbits of water molecules in a deep-water wave.

STEP 1: Draw a water molecule and its orbit

1. DRAW: Draw a small circle to represent a water molecule. Then draw a larger circle to represent its orbit. Select both circles and set their horizontal alignment to ‘centre’, and vertical alignment to ‘top’.

Small circle (molecule): Fill = solid Line = none Large circle (orbit): Fill = none Line = 50% transparent

OPTIONAL: To make the molecule’s circular motion clearly visible, add a third, smaller circle aligned to the centre of the orbit and a thin vertical line.

Centre circle: Fill = 50% transparent Line = none Line (orbit): Fill = not applicable Line = 50% transparent

2. GROUP: Select all the drawing objects and group them together. Animations will now apply to the whole group.

NOTE: the centre of the GROUP should coincide with the centre of the larger

circle so that the GROUP will rotate around this point when animated.

3. RESIZE: In this step, you will scale the group down to fit nine

orbits on the slide with their sides touching.

HINT: The most accurate method to determine the appropriate size is to draw a horizontal line across the slide, measure its pixel length and divide by nine.

4. CHECK: After resizing check if any line thickness is now too thick.

If so, reformat them now.

NOTE: if you do change any formatting in this step, make sure you realign the molecule with the top of the orbit. This will ensure the centre of the group is the same as the centre of the orbit (large circle). If it isn’t, the animation in Step 2 won’t work correctly.



STEP 2: Copy, paste, preset and animate your water molecules 1. ANIMATION: Set the grouped objects to rotate 360° using the

animation features and check that the group rotates about the centre of the large circle (orbit).

PowerPoint: Set animation to ‘Spin’. Keynote: Set animation to ‘Rotate’.

NOTE: if the orbit wobbles during the animation, go back to Step 4 and realign the molecule with the top of the orbit. This ensures the centre of the GROUP is aligned with the centre of the ORBIT.

2. COPY & PASTE: Copy the group and paste 16 more (the far-left

and far-right molecules should be the same distance apart as in Step 4. All 25 molecules must be aligned and equally spaced.

HINT: If using Keynote and ‘Distribute horizontally’ causes your molecules to spread out off the edge of the slide, draw a guide as follows: draw a vertical line then copy and paste the line so you have a total of 25 lines. Distribute the lines horizontally so they are evenly spaced and use them as a guide to align the molecules.

3. PRESET ORBIT ANGLES: Every molecule’s position in a wave is

rotated slightly more than the next. In this model, there are 25 molecules. Molecule 1 is already preset to 0°. Molecule 25 is rotated by a full 360° (compared to Molecule 1) so it doesn’t need to be rotated. The remaining 23 molecules in between need to be preset. Each molecule is rotated by 15° more than the last (i.e., 360 divided by 24). So, Molecule 2 is set to 15°, Molecule 3 is set to 30°, Molecule 4 to 45° and so on. Calculate the rest, then select the molecules one by one and do the following:

PowerPoint: Select the molecule then ‘Format Shape’ and click on ‘Size’. Now type the appropriate angle into the ‘Rotation’ box.

Keynote: Select the molecule then click ‘Metrics’ (the ruler icon in the ‘Inspector’).

4. ANIMATE THE WAVE: Select all the molecules so that the

animation features you set applies to each one. Then set the animation options as follows:

PowerPoint: Select ‘Add effect’, then ‘Emphasis Effect’ and choose ‘Spin’. Set these options: Start ‘With Previous’, Property ‘Two Spins’ (720°), Speed ‘Very Slow’. In ‘More Effect Options’ uncheck ‘Smooth Start’ and ‘Smooth End’.

Keynote: Select ‘Build’ (diamond icon in ‘Inspector’) and select ‘Action’. Set these options: Effect ‘Rotate’, Direction ‘Clockwise’, Rotate ‘720°’, Acceleration ‘None’, Duration ‘5 seconds’.

STEP 3: EXPERIMENT You can make a longer wave by resizing, copying and pasting all the molecules to make a second wave. Align the copied wave with your first wave and animate. Experiment with the speed of the wave by changing the timing of the molecule’s rotation.

ANIMATE

Lesson Plan 22 – Making Waves

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