A Quick Study of Refraction at Spherical Surfaces and Lenses

Refraction at spherical surfaces and lenses can be easier to understand if we explore each term individually. Now, there are numerous phenomena of refraction that occur in nature; some of them include the glare of stars, pre-sunrise, post-sunset, etc. The ability of lenses to converge or diverge the rays of light passing through them is predominantly because of the working principle of refraction. Sometimes, we often see that a pencil appears broken when it is immersed inside a water container, say a beaker. Similarly, we can explore various incidents caused by refraction around us. This phenomenon occurs when there is a change in the route of light when the ongoing medium differs, i.e. the medium in which light travels gets changed. Note that this change happens at the periphery of both the mediums.

Refraction at Spherical Surfaces and Lenses

Refraction at spherical surfaces can occur in two ways, i.e. when the light goes to a denser medium from a rarer medium—which makes the light shift about the normal or when the light goes to a rarer medium from a denser medium—which makes the light shifts off from the normal. These spherical surfaces are the lenses that can be a part of a sphere. Spherical mirrors are one such example of a spherical surface that allows the light falling on them to reflect. The main goal here is to study refraction at spherical surfaces and lenses. The spherical surfaces can be classified into two types: convex and concave. 

Convex Spherical Surface

These surfaces are generally curved outwards. These are also called converging or biconvex lenses. These are thinner around the edges and thickest in the middle part of the spherical surface or lens.

Concave Spherical Surface

These surfaces are generally curved inwards. These are also called diverging or biconcave lenses. These are thicker around the edges and thinner in the middle part of the spherical surface or lens.

Application of Refraction at Spherical Surfaces and Lenses

There can be numerous applications of refraction at spherical surfaces and lenses, some of which are listed below:

1. One of the basic uses is determining the direction of light travelling through various lenses.
2. It helps determine the change in refractive index when the light is made to change its travelling medium.
3. We can derive a formula by grouping the relations of refraction at spherical surfaces. 

Sign Convention of Refraction at Spherical Surfaces and Lenses

Here’s a breakdown of eight basic sign conventions: 

1. All the distances are calculated by taking the optical centre of the lens as a reference point.
2. When the incident ray’s direction and distance measured are the same, we get a positive value.
3. When the direction of the incident ray and the distance measured are not the same, we get a negative value.
4. The distance is positive when measured perpendicular (upwards) to the main axis.
5. The distance is negative when measured perpendicular (downwards) to the main axis.
6. There’s a rule to place the object, i.e. it is always on the left side.
7. Convex/Diverging lenses have a focal length greater than zero.
8. Concave/Converging lenses have a focal length lesser than zero.

Examples of Refraction at Spherical Surfaces and Lenses

There are many examples; some of them include:

Camera

Whenever someone clicks a picture, light waves get refracted from the object and enter inside the camera through the lens of a camera. The medium changes; thus, refraction takes place and allows the light to focus at a particular point 

Microscope

In a microscope, we see a tiny sized object. This instrument helps us in the investigation of numerous minuscule species. Indeed, refraction additionally assumes an immense part in the magnifying instrument. At this point, whenever someone looks through the magnifying instrument, light enters his/her eyes after refraction from the perspective of the element inside the magnifying instrument.

Indeed, the focal point present in a magnifying instrument is circular; however, dissimilar to a camera or binocular magnifying lens, it expands a picture of little species so that the image is noticeable to our naked eyes.

Telescope

A telescope is used to see objects in space. The lens here is spherical and the lightwave gets refracted when the change of medium occurs.

Contact lens

Eye refraction is how the force of eyeglasses or contact focal points is determined. This estimation depends on the amount of the focal point the eye possesses to twist light beams to handle visual upgrades. This is communicated in the estimation of distance and clearness. Refraction tests (also known as vision tests) are usually performed as part of eye tests. It lets the doctor determine the exact amount of prescription that a patient will need for his or her glasses or contact lenses.

Water Droplets

The best example so far is the water droplets. Have you ever wondered how the rainbow is formed? Well, it forms because of the water droplets in the atmosphere. After all, water droplets disperse the white light consisting of seven colours from the sun into respective seven colours. This is the main phenomenon behind the formation of the rainbow.

Conclusion

All of us have used the circular focal points in our lives somehow. The focal point we use in exhibitions or the reflection of our vehicle are all a circular surface. Inward focal points just make virtual pictures. After the beams are refracted, they never unite; thus, there will be no creation of real pictures. Medium alludes to space where light waves travel. Different mediums have an alternate power and hence when a light wave goes into a second medium with high or low thickness, light waves get scattered.