How does a magnifying glass magnify? What is its secret? I looked into this recently and was amazed to discover that it works by playing on the human delusion that the world is just as it appears. A magnifying glass leads to a dangerous mind-game!
When you want to look at something very small, you have to move your eye closer to it, but there is a limit to that strategy. You can move a sheet of paper closer to your eyes but at some point it is too close for you to focus the lens of your eye on anything. For ordinary newsprint that distance is about 10 inches for me. Closer than that and the print is just a blur. The lens of the eye has a variable focal length, but it has limits.
Incoming light rays are bent by the lens at the top and the bottom, but pass straight through the middle. That’s how a lens works. The resulting image on the back of the eyeball is upside down, but we are so used to that, we don’t even notice it and we see the world as right-side-up.
To get a better look at a small object, we insert a magnifying lens between the eye and the object.
The magnifying glass is held close to the small object, so in the drawing above, the light rays from the object are diverging outward, so much so that an eyeball placed that close couldn’t bend them down to the scale of the retina (couldn't focus them).
The lens of the magnifying glass bends the rays of light just enough so they fit into the lens of the eye, which can take it from there and focus the object. You can move the magnifying glass back and forth until you find that good distance.
So now your eye can focus the object but why does that make the object seem bigger (magnified?). That’s where the mental delusion comes in. As far as the eye is concerned, if light rays come in at that angle, at that distance, they must be coming from a much larger object. The dashed lines show what the eye “assumes” about those light rays and where they came from.
The eyeball is not very smart and does not understand the optics of a magnifying glass. It only knows, from its whole life of experience, that when light rays come in at that angle, at that distance, the object is large. That is the message it sends back to the brain.
Consequently, when using the magnifying glass, we see the object as much larger than it really is, out of “eyeball habit.” THERE IS NO LARGE OBJECT out there. We see a magnified large object that does not exist! The actual object is the same size it always was. But by tricking the eye, we delude ourselves into seeing an imaginary larger object.
The larger, magnified object is utter fantasy, but we don’t interpret it that way. We implicitly assume that we are looking right at an actual object that just happens to be enlarged. As if objects in the world could really be enlarged on demand!
That’s not how the world works. Things are the size they are. They do not get larger because we wish them to. So why do we accept without worry that we have just magically enlarged an object? A magnifying glass promotes an incredible delusion!
Magnifying glasses should be regulated by the government. We cannot allow children to use magnifying glasses! A magnifying glass is far more dangerous in distorting the mind than any hallucinatory drug.