Ray optics-convex lens physics

What is a convex lens?

It is common for an optical lens to have two spherical surfaces. It is a convex lens if those surfaces curve outwards. These lenses have a thicker centre and a thinner edge.

The lens can also converge light from the outside and focus it on a focal point on the other side. The focal length of a convex lens is the distance from its centre to its focal point. A converging lens focuses a parallel light beam into a single point.

Roger Bacon, an English monk, and scientist wrote about his experiments with convex lenses to correct vision in 1267, recommending its help to older people.

Uses of convex lenses

Magnifying glasses

A magnifying glass is used to make an object larger than it actually appears.  When the distance between the lens and the object is less than the focal length, the object magnifies. The magnification is highest when an object is at the focal point. You may have noticed that you need to get the glass close to the object to achieve a decent magnification. The point where light rays parallel to the principal axis are brought to a point called the focal point of the convex lens.

Eyeglasses

When the natural lens in the eye cannot focus light on the retina, a person has difficulties seeing objects. Hyperopia is a condition in which a person can’t see objects close to their eyes. However, the individual can see distant objects. Far-sightedness is another name for this condition. This problem is due to the ciliary muscles’ inability to change the focal length of the eye lens. The light emitted by the objects has a focus beyond the retina. Better vision is possible by placing a convex lens in front of the eye, which causes light rays to converge and focus directly on the retina.

Optical microscopes

An optical microscope can easily view small microfibers, bacteria, microparticles, and micro-textured surfaces. A convex lens may magnify objects, and a basic microscope’s magnifying power increases by combining three lenses. Compound microscopes contain an even more significant number of lenses to boost the microscope’s magnifying capability for viewing microorganisms.

Projectors

Projectors are optical devices that display images or videos on big screens. The goal behind a projector’s operation is to magnify the picture or video shown on the screen. The lens magnifies and inverts the image it creates and loads the film in an inverted position to compensate for the inverted image created.

Optical camera

Convex lenses focus and magnify pictures in cameras. We can adjust the camera’s magnification by moving the convex lens. We’re changing the focal point to gain greater magnification with this action and used convex lenses in video cameras and webcams.

Human eye

When you can see something because it emits light or can reflect it, the object’s light enters our eye and processes it into an image. Light enters our eyes through the cornea. Nature’s use of convex lenses is a great example of this. Using our eyes’ natural lens, we can see clearly. The retina is a light-capturing tissue that looks like a screen. The retina has different cells that convert light into neural signals. The brains process these neural signals. The lens’s inability to focus light onto the retina causes farsightedness or near-sightedness.

Telescope

The telescope helps in viewing objects that are extremely far away, such as planets in our solar system. Refracting and reflecting telescopes are the two types of telescope. Reflecting telescopes work on mirrors, whereas refracting telescopes use convex lenses. The telescope has two convex lenses, and the primary lens focuses all the light, while the second lens magnifies it.

Multi-junction solar cells

You can use convex lenses as concentrators to focus more light radiations, increasing solar cells’ power output.

Binoculars

Binoculars magnify images of faraway objects—used in the military, stadiums, and bird watching. The working principle of a binocular is similar to a telescope.

What is the convex lens formula?

The convex lens equation is 1/f = 1/v – 1/u, where, f is the focal length of a given convex lens, u is the distance between the object and convex lens and v is the distance between image and convex lens.

Conclusion

Convex lenses may create real and virtual images and capture a true picture on a screen projected in front of the lens. Convex lenses are the only ones that can produce real images. So, in projectors of movie theatres, to display magnified pictures onto screens, convex lenses are used.

Convex lenses may also produce virtual pictures, which we use as magnifying glass. For vision correction also, people use convex lenses.