Discover how you can build your very own solar marshmallow melter. Not only can you enjoy making delicious molten marshmallow using solar energy, you can also save money on electricity.
You will need
• Large Fresnel lens
• Tin foil
• Skewers or a toasting fork
In this project, we are going to collect the sun’s energy from a large area, and focus it to a point in order to create localized heating.
One way of collecting the sun’s energy from a large area is to use mirrors.
In order to perform this experiment, we are going to need a Fresnel lens.
Put the marshmallow on a skewer, and rest it on the sheet of tin foil. We are going to use the Fresnel lens, to focus the sun’s rays onto the marshmallow. When you look out of your window, there is no magnification or reduction of the image-the glass does not act like a lens; however, you will notice when looking through the lens (not at the sun!) the image appears much bigger and magnified. Why is this? If you look closely, you will see a series of concentric circles in the lens. Now think of a magnifying glass – it is round and circular, and “bulges” in the middle. If we look at the glass from side-on, we can see that both sides of the lens are curved – but there is also a lot of glass in the middle! A Fresnel lens “removes” some of the glass from the4 middle, and flattens the lens onto a sheet. Each little concentric ring that you see on the flat Fresnel sheet, is a section of lens curve.
Look at where the sun is in the sky, and hold the Fresnel lens perpendicular to an imaginary line between the sun and your marshmallow. Move the lens to and from along this line, and observe how the focused beam of solar energy changes on your marshmallow. After a little bit of time, focusing the sun onto the marshmallow, you should see the candy begin to toast! No fire required – just the power of the sun!