Dr. Seahorse Sees the Invisible

The Sun provides light and heat. You can see the light, but what about the heat? In this experiment, you can make the heat visible.

• Mobile phone with built-in camera
• TV remote control

Learn of the existence of different kinds of light, made of many different colours, some visible and others invisible to our eyes. Understand specifically what infrared light is, and learn how we use it in everyday life.

Sunlight is a mixture of many different colours. You can see this when the sunlight is refracted by raindrops — a rainbow appears in which all of the different colours are neatly arranged. The Sun also emits light that our eyes cannot see, such as infrared radiation. Our eyes are not capable of seeing infrared rays, but we feel them sometimes when they heat our skin.

Invisible infrared light is also used in remote controls to transfer signals to the TV. The funny thing is that, unlike our eyes, a mobile phone camera can ‘see’ this light! The camera can also see the infrared light coming from the Sun. However the Sun emits so much visible light compared to infrared light that it’s extremely difficult see the infrared light. Therefore, astronomers wanting to observe the Sun and stars in infrared light must use special cameras.

Step 1

Press any button on the remote control and look for a light flashing in the front of the controller. Repeat this, but this time look at the flash through your mobile phone camera. (Image 1) What do you see?