Tracking Light Levels – Are Your Sunglasses Really Working?

 

🕶️ Tracking Light Levels – Are Your Sunglasses Really Working?

We put on sunglasses and assume they’re protecting our eyes. But how do we know they actually reduce harmful light? What’s the difference between a dark lens and a UV-protective one?

This summer, let’s bring physics outdoors and put sunglasses to the test — using a PASCO wireless light sensor or even a mobile lux meter app.

Spoiler: Some sunglasses look stylish but block less light than you'd think!

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☀️ 1. Light Intensity – What Are We Measuring?

Light intensity is measured in lux, which represents the amount of light hitting a surface.

• Direct sunlight = up to 100,000 lux

• Office lighting = 300–500 lux

• Overcast daylight = ~1,000 lux

When we wear sunglasses, we expect a big reduction in lux reaching our eyes. But not all lenses are created equal...

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🧪 2. The Outdoor Experiment

What you need:

• PASCO wireless light sensor

• A range of sunglasses (cheap vs expensive)

• Optional: UV torch and UV-sensitive paper

• Data logging app or mobile device Sparkvue 

Method:

1. Place the light sensor under normal outdoor sunlight (no lenses). Record the lux reading.

2. Hold different sunglasses between the sensor and the sun. Record the drop in lux.

3. Repeat in shade, near reflective surfaces, and with different lens colours.

Bonus: If your sensor also records UV levels, you can test for actual eye protection, not just brightness reduction.

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🔍 3. Analysing the Results

Some surprising things you'll learn:

• Darker lenses ≠ better protection

• Some budget sunglasses reduce brightness but not UV exposure

• Polarised sunglasses significantly reduce glare, but not necessarily lux

• Mirror lenses often bounce light away from the eye but let more ambient light through

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🧠 4. What Students Learn

This simple practical links beautifully to:

• GCSE Physics – light, intensity, reflection, absorption

• A-Level Physics – wave behaviour, sensors, data logging

• Science skills – collecting, analysing and comparing data

It also encourages:

• Consumer awareness

• Critical thinking about product claims

• Real-world applications of light physics

💡 Tip: Plot a bar chart of light reduction for each pair of glasses. The results might surprise you — and your students!

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📷 5. Extension Ideas

• Use a polarising filter to demonstrate how polarised sunglasses block glare

• Try using photochromic lenses and record how they darken over time in UV

• Test tinted car windows, hats, or clear UV-blocking lenses

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🎓 Science Outdoors, Made Easy

At Philip M Russell Ltd, we believe science happens everywhere — not just in a lab. With wireless sensors, simple experiments, and a curious mindset, we help students explore physics in the real world.

Whether it’s tracking sunlight in the garden or building graphs from everyday items, we teach GCSE and A-Level Physics through discovery and data.

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📅 Now enrolling for 1:1 Physics Tuition – online and in-person, in the Lab
With experiments, real data, and clear explanations.
🔗 www.philipmrussell.co.uk