Exploring light and shadows

by Wendy Sadler

Now the days are getting longer and the rain is finally coming less often (unless you live in Cardiff of course!) we like any opportunity to get outside and work in the sunshine*. This is a great activity to help children learn about light, get them taking measurements and making tables, and possibly create a piece of science art for your playground all in one go!

*Don’t forget your sun cream of course!!

Human sundial


Zoë becomes a sundial! Photo: science made simple (All Rights Reserved)

You will need

Chalk (jumbo outdoor chalk would be ideal)

A measuring tape or meter rule

A willing volunteer who can stand still for a minute or two

Enough sunshine to cast a shadow!


Human Sundial!

Shadow moves over time. Image: science made simple (All Rights Reserved)

What to do

First thing in the morning (if the sun is out) go out into the playground with some chalk. Find a good spot where there won’t be any shadows from trees or fences and make a cross. Choose a volunteer to be the human sundial and ask them to stand on the cross. Get another child to draw around the shadow and then ask all the children to use a tape measure to see how long the shadow is.






Back in the classroom, create a table like this:

Time taken (Hours/minutes)     Length of shadow (cm)

9 hr 10 mins                             87cm

Every 30 minutes or so you can send another team into the playground to repeat the experiment and bring back another measurement. You must use the same person as the sun dial to be a fair test. Ask the children why it matters to use the same person each time?

Over the day (or a number of days if the cloud gets in the way!) build up a table of measurements as a class and see what the pattern looks like. You could use an excel spreadsheet to turn the table into a graph to show how scientists turn numbers into shapes to help make sense of them.

Class discussion

Whilst doing the activity ask the children where the light in the world comes from? Is it different when we are outside or inside? Why do we get shadows and why do they change length throughout the day?

Misconceptions of light and shadows

It’s a fairly common misconception in primary children that they see things because light comes out of our eyes, and that shadows are also somehow made from our bodies ‘giving out’ dark. Ask whether the children think they have a shadow when in a dark room to try and establish that you need a light source and an object to block it to make a shadow. In the case of this sundial the sun is the source of the light and the person in the middle is blocking that light so we can see her shape in a shadow on the ground.

The other misconception you can talk about with this activity is that the sun moves across the sky. It may be too tricky to get into a model of how the planets moves around the sun, but you can introduce the idea of the earth spinning once in one day and that is why we get roughly half daytime and half night time. When our country is turned away from the sun and it is night, another country on the other side of the world can be in bright sunshine. Use a globe in the classroom to show this using a desk lamp to represent the sun.

No sun? There’s still shadow fun!

If you’re feeling really arty – you could try and create your own shadow artwork using three different coloured light bulbs in slightly different positions like we do in our non-verbal theatre show ‘The Experimentrics‘ (shortly to be touring Wales!). You can even buy a small piece of kit to show this in the classroom from suppliers Phillip Harris here.

coloured shadows visualise science show

Coloured shadows demonstration in ‘The Experimentrics’ Phoso: Kiran Ridley (All Rights Reserved)

Shadows and the seasons

Finally, if you are able to use more permanent paint on the playground (so it doesn’t get rained off), you could build up a sequence of shadows from now until Autumn and see if the students can work out from the patterns which day of the year is the longest one. It should create an interesting piece of science-art!

Curriculum links

Key stage 1/Foundation

  • observe changes across the 4 seasons

  • observe and describe weather associated with the seasons and how day length varies

Key stage 2

  • recognise that shadows are formed when the light from a light source is blocked by a solid object

  • find patterns in the way that the size of shadows change


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Posted in Activity, Physics, Primary