Making Waves

Scene: Surf's Up (and Down, and Up Again)

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Interactive: A Wave with Words

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Lesson: Modeling Mechanical Waves

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Demo: Ripple Tank

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Lab: Sound Stations

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Conversation: Waves of Danger

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wave

noun – a moving disturbance

Let's just stay put and wait for this wave to go by.

frequency

noun – the rate at which something repeats over time

I go to this beach with some frequency, because the waves also come with great frequency. More waves, more surfing!

amplitude

noun – measurement of highest point (or lowest point) in a wave when compared to its resting position

The amplitude of a wave increases with more energy.

trough

noun – the area around the lowest point of a wave; sometimes called a “valley”

While waiting for a wave to surf, it can be very relaxing to rise with each passing crest and slide into each passing trough.

crest

noun – the top of something; the area around the highest point of a wave; sometimes called a "peak"

Surfers stay a little ahead of the crest of a wave and slide down the front of it.

wavelength

noun – the distance in a wave between one crest and the next, or between two consecutive troughs

Waves with high frequencies also have shorter wavelengths.

compression

noun – the state of being squeezed or pressed together

Sound waves are compression waves. When we clap our hands, the air between our hands gets compressed. The air molecules bump into each other, creating a vibration that travels through the air as a longitudinal or compression wave.

medium

noun – a substance (like a solid, liquid, or gas) that the energy of a wave can travel through. In the example above, the medium is a flag.

All mechanical waves need a medium—such as water, air, or metal—to travel.

vibrate

verb — to move back and forth (or up and down) around a point; to shake with small, rapid movements to and fro.

Instruments make sounds when some parts of them vibrate, which moves the air molecules inside or around the instrument.

period

noun – a length of time

The period of one wave is the time it takes two crests to pass a point.

diffraction

noun – bending or turning of a wave around obstacles, or spreading out after the waves pass through small openings

Wave fronts bend as they go through a narrow opening, demonstrating diffraction.

refraction

noun – bending or turning of a wave as it goes from one medium to another, for example a light wave bending from air to water

Wave fronts bend as they approach a beach, demonstrating refraction.