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How Do Binoculars Help Us?

Last Updated: 06.12.21


If your child asks you about binoculars, you might want to check it out here to make sure you get the answer right. Created by using two lenses, binoculars have found quite a lot of uses for themselves in activities ranging from bird-watching all the way to police work and spying.



What are binoculars?

Since walking on the Moon or staring an elephant right in the eye are pretty hard to come by for most people, binoculars are the next best thing in their attempts to accomplish such difficult feats.

Together with telescopes, these cool gadgets are based on the science of optics and use lenses which pull some pretty clever tricks on light to get us a much-zoomed-in image of our focus point.

However, since most people already know this basic information, let’s find out how exactly does this entire process work and why is it so important to such a great number of areas nowadays.


Binoculars use lenses

As you know, lenses come in all shapes and sizes. For instance, the giant Fresnel lens surrounding a lighthouse lamp is designed to concentrate the light into a parallel beam, allowing onlookers to see it at a great distance.

The lenses in binoculars, however, concentrate on doing the exact opposite job, focusing light rays which are far off so whoever is watching can see distant things more clearly. In science, the way light bends when going from air to a different material such as glass or water is called ‘refraction’.

This process is key to how lenses work which makes it key to how binoculars, telescopes, and even glasses get the job done. However, you might ask, how do we get from light bending in the water to a pair of binoculars in our hands which lets us do cool things like study the moon?

Apparently, water sitting in a glass has a straight upper edge, even though it is very slightly curved. If somebody were to place a glass on top of a newspaper and look straight down, the paper looks like nothing out of the ordinary because the top of the water is effectively straight. 

However, if the water had a curved upper surface, a very simple experiment would show you that the new print would look magnified, therefore demonstrating why binoculars and other tools with lenses work the way they do.



Types of lenses

In plain English, a lens is a curved piece of glass shaped a little bit like a lentil. In fact, that’s where it gets its name from because the word ‘lens’ comes from the Latin word for ‘lentil’. 

When light rays hit a glass lens they will immediately slow down and bend, causing two types of possible effects: if the lens curves in a dome-like fashion, so its outside is thinner than its middle, we call it a convex lens. As the light enters this type of lens, it bends in toward the middle and that means the convex lens is bringing those distant rays into close focus.

Therefore, another name for this is a ‘converging’ lens, simply put because it makes the light rays come together or, in other words, converge. Looking at things through a convex lens always makes them appear bigger than they are so that is why these types of lenses are used in things like magnifying glasses.

On the other hand, another kind of lens will curve the opposite way, with the middle being thinner than the outside, and this is called a concave lens. What this does is it makes light rays spread out, just like the lines of a firework. If you can’t see it, imagine light rays coming into the small concave lens and then shooting out in all directions. 

This is why they are sometimes called diverging lenses because they make light rays shoot out or, in other words, diverge. This type of lens has great use when it comes to movie projectors, making the light from the film spread out and cover a bigger area when it hits a plain, solid wall.


How binoculars work

After these explanations, you can probably see where we are going with this. If you want to be able to look at something in the distance, you can use two convex lenses which you place one in front of the other.

The first lens will catch the light rays from the far-away object and create a focused image a short distance behind the lens. Because it is nearest to the object you want to look at, this lens is called the ‘objective’. 

The second lens will pick up the image that the first one brought and magnify it, just like our newspaper was magnified in the example above. If you put the two lenses in a closed tube, just say ‘Presto!’ and there you go, you have your own telescope. If you’re a DIY person, you can make one quite easily with a couple of magnifying glasses and a cardboard tube.

Binoculars, simply put, are two telescopes side by side, one for each eye. However, there’s a catch to this because when light rays from a distant object pass through our convex lens, they cross over. This is the reason why far-away things sometimes look upside down if you watch them through a magnifying glass.

Since the second lens does not sort out this problem, binoculars come equipped with a pair of prisms, which are large wedges of glass located inside them and able to rotate the image through 180 degrees.

The first prism will rotate the image through 90 degrees, effectively flipping it onto its side, while the second one repeats this process so the two of them together are actually turning the image upside down.

The next time you wonder why the binoculars are so heavy in your hand, remember it is because of these prisms. An alternative to binoculars would be using field glasses, which only flip the incoming images by using the lenses. However, because there are no prisms, while the glasses are smaller and lighter, the image quality is poorer.



What are binoculars good for?

Nowadays, binoculars have been found to be the perfect item with a wide range of applications and uses. Of course, the ones that come to mind are events for outdoor enthusiasts such as bird watchers, hunters, and hikers.

Furthermore, you can also use them in places such as concerts, sporting events, or other special occasions which require you to see something happening at quite a little bit of distance and are therefore ideal to put your new pair of binoculars to good use.

However, boaters can also benefit from using them with activities like whale watching, where you really have to pay attention all the time. If you’re into this, remember to get some waterproof binoculars so your view isn’t spoiled in the most important moment by a bit of sea spray.

Law enforcement officials and people working as private investigators should always have a good, sturdy pair of binoculars on hand since they never know when they will need to take a closer peek at something.

Even reporters and journalists may sometimes benefit from having a pair of these bad boys since there are plenty of situations where the press is held at a distance and a closer look might prove to be invaluable. 


Some tips for buying binoculars

The number one tip for buying a new pair of binoculars would be to adapt your purchase to whatever you need it to do. For instance, aficionados doing bird watching will undoubtedly need a more expensive product while people who simply want to spy on their neighbors can also make do with a pair of cheap field glasses.

Also, educate yourself enough to know that ‘more magnification’ does not necessarily mean ‘better binoculars’ because the more the lenses magnify, the more impact your hand movements will also have.

Furthermore, binoculars are always described with two numbers separated by an x. The first number will be the magnification, so if the number in question is 8, that means those binoculars can magnify up to eight times. The second number will be the size of the objective lens and it will be represented in millimeters.



Ioana Moldovan

Ioana’s professional experience in the optics field has helped her understand the value of passing her knowledge forward. Her curious personality helps her gather useful information for her readers and her goal is to make technical information fun and accessible to everyone.

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