Stella and Selma are out at sea on a treasure hunt. But the map has some tiny symbols that are difficult to read. And all the islands are too far away for the girls to see where to go next! The human eye is one of the most important sense organs in our body. Human eyes react to light and allow us to experience the world around us through visual images.
But eyes have limitations — we can’t see extremely small or distant objects, well. To see things better and clearer, we invented devices that process light and enhance images. We call these devices optical instruments. Optical instruments make use of lenses made of glass or other transparent material. Lenses concentrate or disperse light rays in a way that makes objects appear bigger or smaller.
The simplest optical instrument consists of a single lens, usually mounted in a frame with a handle — a magnifying glass. The lens in the magnifying glass curves outwards — it is thicker in the middle than at the edges. It’s a convex lens. Convex lenses make objects look larger — magnified. A magnifying glass works great for close distances — it can be used to read very small text.
Or to examine details of things such as a treasure hunt map! However, if you point a magnifying glass at an object that’s far away, it won’t work very well. The object will appear closer and bigger, but the image will be blurry. What can you do to see distant objects better? Hm, what if you combine a couple of different lenses in a row…?
Craftsmen and scientists in the early 1600s must have asked themselves a similar question. This resulted in the invention of the telescope. The first telescopes used two lenses enclosed in a tube. At the end of the telescope pointing at the object, was a magnifying convex lens. At the other end, close to the eye, was an inward-curved concave lens which helped focus the image.
Over time, optical telescopes improved, and different combinations of lenses and mirrors allow us to observe distant objects. If you put two telescopes next to each other and look through both at the same time, you get another optical instrument — binoculars! Binoculars use the same principle as telescopes, but you can use both your eyes! Each eye gets a slightly different viewpoint, so the final image has depth — it’s 3D! Binoculars come in all shapes and sizes and are used for many things, from observing nature to finding things far on the horizon!
Telescopes and binoculars give us a significantly magnified view of very distant objects. What about the things that are way too small to be seen with the naked eye, or even with a magnifying glass? For that, we need a device that can magnify the image hundreds of times, and doesn’t take as much space as large telescopes. Combining a number of concave and convex lenses, microscopes allow us to see detailed images of things — tiny bacteria or single cells. And wouldn’t it be great if we could capture all these images we see?
We can — using another optical instrument — a camera! Cameras are built in a way that allows us to adjust how much light passes through the camera's lens. The light that passes, falls onto a light-sensitive surface, such as photographic film or a digital sensor. This way, you can capture whatever you see as a photograph or record it as video! Reading maps and scanning the horizon is much easier with the help of optical instruments, like a magnifying glass and binoculars!
Don’t forget to take photographs once you find the treasure!