Microwaves

 Using the @Lascells Microwave transmitter and receiver to demonstrate how the waves that come out of the transmitter are polarised, so only one polarising filter is necessary to cut out the beam to the receiver.

Polarised Science: Exploring Reflection and Refraction with Lascells Microwave Kit

One of the most satisfying experiments in the physics lab involves something we can't even see — microwaves. Thanks to the brilliantly designed @Lascells microwave transmitter and receiver, students can visualise the invisible and explore the fascinating properties of electromagnetic waves using everyday equipment.

Let’s walk through how this simple but powerful setup can be used to demonstrate polarisation, reflection, and refraction — all without needing to see the waves themselves.

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🔦 Seeing the Unseen: Polarisation with Microwaves

Microwaves, like light waves, are transverse waves, meaning the oscillations occur at right angles to the direction the wave travels. The waves coming out of the Lascells microwave transmitter are already polarised — the electric field oscillates in a fixed direction, vertically or horizontally depending on the orientation of the transmitter.

This makes the first part of our experiment refreshingly straightforward:

• Place the receiver in line with the transmitter and measure the signal strength.

• Insert a single polarising grid between the transmitter and the receiver.

• Now rotate the polariser slowly through 90 degrees.

Result? The signal drops from full strength to nearly zero!
This dramatic effect shows that the microwaves are already polarised. Just like wearing polarised sunglasses blocks glare from horizontal light waves, our grid blocks microwaves when its wires are perpendicular to the wave’s electric field.

No need for a second polariser here — the transmitter has done half the job for us.

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🪞 Reflecting on Waves: Using Metal Plates

With polarisation sorted, it's time to have a look at reflection.

Using flat metal plates, we can easily create microwave "mirrors". Here’s how:

1. Set up the transmitter and receiver so they're not pointing directly at each other — no signal should be detected.

2. Now place a flat metal plate at a 45° angle to the beam coming from the transmitter.

3. Place a second metal plate at a right angle to the first, so it reflects the wave again — this time towards the receiver.

This setup mimics a periscope — but instead of bouncing light, we’re bouncing microwaves. The receiver should now detect a strong signal again.

For students, this is an eye-opener. It shows that microwaves reflect off metal surfaces just like light reflects off a mirror, obeying the law of reflection: angle of incidence = angle of reflection.

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🌈 Bending the Rules: Refraction with Acetate

Next, we turn to refraction, the bending of waves as they pass from one medium to another. Since microwaves can pass through many materials that are transparent to them (like acetate sheets), we can investigate how the wave changes direction — even though we can’t see the wave itself.

Here's how to demonstrate it:

1. Position the transmitter and receiver at an angle, with an air gap between them — no signal should get through.

2. Now insert a large sheet of clear acetate at the correct angle so it forms a medium between the two.

3. The microwaves now travel from air, into the acetate, and back into air, bending as they go.

You should see the signal strength increase when the acetate is correctly placed — demonstrating refraction.

To extend the activity, you can:

• Measure angles of incidence and refraction (using protractors and careful alignment).

• Discuss how the speed of microwaves changes as they pass through the acetate, causing the wavefront to bend.

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Bonus Idea: Standing Waves and Interference

While you're at it, try moving the receiver slowly back and forth. You'll likely find nodes and antinodes in the signal strength — evidence of standing waves and interference patterns caused by reflections. Another elegant link to wave physics.

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Why This Matters

This trio of demos — polarisation, reflection, and refraction — gives students a hands-on understanding of wave behaviour. It also makes the abstract more concrete. No need for computer simulations or animations. With the Lascells microwave transmitter and receiver, the physics speaks for itself.

Whether you're teaching GCSE or A-level Physics, this is an experiment set that delivers real "aha!" moments — with invisible waves made visible through clever science.

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Do you use the Lascells microwave kit in your school or lab? Share your experiments with us on X (formerly Twitter) @pmrscience or in the comments below.