Light Waves!

Light travels as waves, a bit like ripples in a tank of water.

waves page header

But unlike sound waves, light waves can travel through empty spaces. This is how we can see stars even though they are billions of miles away.  Light waves also travel much faster than sound waves, three hundred million kilometres a second in fact! Which is why you see lightning before you hear the bang.

light waves

Let’s imagine those light waves rushing along at super speeds, faster than anything else in the universe. What happens when they meet an object?  Well, if the object is black then all the light will sink in.  And if the object is shiny, lightly coloured or reflective, then lots of the light will reflect back, that’s how we can see ourselves in a mirror or in shiny surfaces.

The light all around us is white light, but it contains many different colours.  When white light hits certain objects, such as clear glass prisms or even raindrops, sometimes you can see many of them at once, just like a rainbow! There are seven colours of the spectrum, and they are red, orange, yellow, green, blue, indigo and violet.

visible light spectrum

There are three primary colours in light, red, green and blue. When light in these colours are added together they make the secondary colours. For example, when you mix red and green light together, you make yellow. But when you add all three primary colours add together, you make ‘white light’.

When light hits a surface, some of it is absorbed and some of it is reflected back.  The light that is reflected is the colour of the object in that light.  So a blue object, like your jeans, absorbs all the colours except blue because it reflects blue light.

And here’s something else you might not know! The light falling on objects can change the colour of things too.  If you put some blue cellophane over a torch at night, everything in your room will look blue.  And if you look at a green car in the street under an orange streetlight, it can appear to be very different to how it looks in daylight.

That’s because the light hitting the car is missing some of the colours and so even if the car could reflect them, in certain situations, it can’t.  The colour has changed.  Switch off the lights altogether and everything goes dark!

So you can see light waves help shape our world, both helping us to see and to experience colours too!

Click below to learn all about waves!


So You Want to Know About… Waves? is supported by The Institute of Physics 

iop,-institute-of-physics---uws-(1)