Lens - PDF

Speaker 1 ([00:33](https://www.happyscribe.com/transcriptions/d17db77a006a4358ba94f4c5036582ab/edit?position=33.21&utm_source=happyscribe&utm_medium=document_deep_link&utm_campaign=editor_copy_section&utm_content=d17db77a006a4358ba94f4c5036582ab))\ So what is a lens in the first place? A lens is a t...

Speaker 1 ([00:33](https://www.happyscribe.com/transcriptions/d17db77a006a4358ba94f4c5036582ab/edit?position=33.21&utm_source=happyscribe&utm_medium=document_deep_link&utm_campaign=editor_copy_section&utm_content=d17db77a006a4358ba94f4c5036582ab))\ So what is a lens in the first place? A lens is a transparent glass of plastic with curved sides that can bend lightways as they pass through it and change direction. This process of redirection of light rays as they pass from one medium to another is called refraction. But how this light will bend depends upon the type of lens that comes in two main forms, convex lens and concave lens. Though both the lenses are bordered by two transparent, spherical surfaces, but it\'s fairly easy to set them apart. Yes, in a convex lens, the two spherical surfaces are curved outwards, while in the case of a concave lens, they are curved inwards. Also, a convex lens is thicker in the middle with thinner edges, while the concave lens has a thin center with thick edges. But the vital question is, how do these lenses work? Well, it\'s due to refraction, which, as we learned before, is the bending of light rays in a certain way.\ \ Speaker 1 ([01:56](https://www.happyscribe.com/transcriptions/d17db77a006a4358ba94f4c5036582ab/edit?position=116.2&utm_source=happyscribe&utm_medium=document_deep_link&utm_campaign=editor_copy_section&utm_content=d17db77a006a4358ba94f4c5036582ab))\ This twisting and turning happens in two ways, convergence and divergence. And what do they mean? Well, for that, first we must look into the way both the lenses work. Now, an imaginary ray of light, which is also called an incident ray, is projected on a convex lens at an angle. Then from the point of the incidence, which is the touching point of the ray and lens, we draw line known as normal. Now, from the point of incidence, this ray of light will enter the lens, and because the glass is thicker than air, it will slow down the ray\'s speed and bend it down towards the normal line. Now, once this refracted ray reaches the other surface of the lens and enters the air again, which is less dense than the glass, the momentum pushes the light to continue to refract further as it gains back its speed. And this time it bends away from the normal line. So in short, That\'s how light is refracted by a convex lens. Over here, we saw how a single incident light will act in such a scenario. But in reality, there are multiple rays of light. When these rays pass through the convex lens, they are refracted according to the angle at which they touch the glass.\ \ Speaker 1 ([03:39](https://www.happyscribe.com/transcriptions/d17db77a006a4358ba94f4c5036582ab/edit?position=219.73&utm_source=happyscribe&utm_medium=document_deep_link&utm_campaign=editor_copy_section&utm_content=d17db77a006a4358ba94f4c5036582ab))\ Further, they meet at a common point, also known as convergence at a single point or focal point, as rays of light continue in a straight line beyond the focal point to project an image on a screen. Now, let\'s look at the concave lens which works exactly opposite that of the convex lens. Yes, if the incident rays from a point object are projected towards a concave lens, then after refraction, they do not converge at a single point, but diverge, meaning they go away from each other. Because of this, instead of forming the image on the other side, these rays extend backward and meet at a certain point behind the lens. So a virtual image appears at this focal point. Trivia time. Did you know the distance from the The center of the lens to the focal point is called focal length. Also, the focal length of the lens and the distance between the lens and the object will cause the image to be smaller or larger than the original object.