KS2 Science: How effective are different liquids at blocking out UV light?

Primary resources > KS2 Science > Experiments in controlled environments

Video summary

Presenters Frankie and Louise are enjoying the sunshine and put some sun cream on to protect their skin from the sun’s harmful UV rays.

But they can’t help wondering does sun cream really work? So, they put it to the test, asking how effective different liquids are at blocking out UV light?

Using UV beads, which contain pigments which react with ultraviolet light from the sun, they carry out a simple comparative test.

They cover three sets of UV beads with sun cream, oil and water, shine a UV torch on the beads to discover which liquid blocks out UV light.

This short film is from the BBC Teach series Experiments in controlled environments.

Teacher Notes

Before Watching

Show your learners a bottle of sun cream. Ask your children why it is important to wear sun cream? Ask them to think about ways that we protect ourselves from the sun? Show them some UV beads – ask them to predict what happens when you expose them to natural light? Explain that they are responding to a special type of light called UV light.

After Watching

Reflect on the results of the investigation. Which liquid prevented UV from reaching the beads? What does this tell us about how sun cream protects our skin? What do they think the SPF number on sunscreen means? SPF stands for sun protection factor. It’s the measure of how much UV gets through the screen. The higher the number, the less UV passes through.

Try the investigation out. You could also try investigating different fabrics – which ones are better at stopping UV light from reaching your skin? You could then use your results to make a sun hat! Or you could test your sun glasses. If you place them over UV beads, do they prevent UV from getting through? Discuss why it is important that sunglasses filter out UV light. It’s important that all sunglasses carry a UV400 mark. This means that the lens is blocking all the harmful UV.

Ideas for further learning

Design an information campaign to share with other people. How can you teach them about keeping their bodies safe in the sun?

Research how flowers use colours and markings in the ultra violet spectrum to attract pollinators.

Key Knowledge

• UV Light – ultra-violet light cannot be seen by the human eye. Some animals, including birds, reptiles, and insects such as bees, can see in the ultraviolet spectrum. Many birds have patterns in their plumage, that are invisible to us humans at usual wavelengths, but can be seen in ultraviolet spectrum by other birds.

For us humans, too much UV light can cause sunburn or cause damage to our eyes. So, it is important to wear a hat and sun screen when outdoors especially in the summer time.

• UV Beads - contain pigments that turn colours when exposed to UV light. UV Beads are the perfect tool for understanding how solar radiation can be harmful and to recognise measures that can be taken to reduce the risks associated with exposure to sunlight.

Developing practical enquiry skills

• Comparative test enquiries - comparative test are an opportunity for children to make comparisons. In this case we are comparing liquids. To set up a comparative test we change one variable, measure another variable and keep all the other variables the same. It is important that we only change one variable so that we know what caused the effect.

• Prediction - a prediction is saying what might happen based during an investigation. When asking learners to make a prediction, it is important to encourage them to draw upon what they already know to support their thinking.

These short film clips support teachers with practical enquiry. They can be both used as a resource for learners to watch at home, or as a stimulus to support learners to plan and conduct their own science investigations. They link to the UK Science curricula.

Light

• Pupils Recognise that light from the sun can be dangerous and that there are ways to protect their eyes.

Science enquiry / Working scientifically

• Pupils should plan different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary.
• Pupils should take measurements, using a range of scientific equipment, with increasing accuracy and precision, taking repeat readings when appropriate.
• Pupils should record data using tables.

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