# What are Convex Lenses? | Don't Memorise | Summary and Q&A

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April 11, 2018
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Infinity Learn NEET
What are Convex Lenses? | Don't Memorise

## TL;DR

This video explains the characteristics and functions of biconvex and biconcave lenses and introduces the concept of refraction and convergence of light rays.

## Key Insights

• π  Biconvex and biconcave lenses have different curved surfaces and thickness variations, distinguishing them in shape and properties.
• π Lenses refract light by changing its direction due to different refractive index values of the media involved.
• π Convex lenses bend light rays inwards, causing them to converge at a focal point, creating a converging lens.
• π Refracted light rays form images when converged at a focal point, allowing for the functionality of lenses in devices like magnifying glasses.
• π Convergence and divergence are two primary patterns of light refraction that can occur through the use of lenses.
• π¨ The refractive index of air is lower than that of glass, causing light to bend away from the normal when it exits a convex lens.
• π Biconvex lenses are considered converging lenses because they focus light rays to a single point, while concave lenses diverge light rays.

## Transcript

In our previous video, we discussed about what a lens is and also its various types. It is bounded by two surfacesβ¦ one of them is spherical and the other? Yes it is spherical or plane! These are the different TYPES of lenses! The two specific lenses that we are going to cover in this course are called biconvex and biconcave lenses. Each one is bou... Read More

### Q: What are the key characteristics of biconvex and biconcave lenses?

Biconvex lenses have two inwardly curved spherical surfaces, while biconcave lenses have two outwardly curved spherical surfaces. Convex lenses are thicker in the center and thinner at the edges, and concave lenses are thicker at the edges and thinner at the center.

### Q: How does a lens refract light?

A lens refracts light when it causes the light rays to change direction as they pass through it. The speed of light changes when it enters a lens, resulting in the bending of the ray towards or away from the normal, depending on the refractive indices of the incident and exiting mediums.

### Q: What is the pattern of light refraction in a convex lens?

In a convex lens, the light rays converge or focus at a single point after refraction. This point is called the focal point, and the lens itself is known as a converging lens.

### Q: What is the main function of a lens?

The main purpose of a lens is to refract light in a specific pattern. Depending on the type of lens, this can include convergence, where the rays meet at a focal point, or divergence, where the rays spread apart.

## Summary & Key Takeaways

• Biconvex and biconcave lenses are two types of lenses with spherical surfaces, where the former is curved inwards and the latter is curved outwards.

• Lenses refract light in specific patterns, namely convergence and divergence.

• When a ray of light enters a convex lens, it bends towards the normal due to the decrease in speed, causing the rays to converge at a focal point.