Optics PDF

A lens is a transmissive optical device that focuses or disperses a light beam by refraction when the light beam passes through a lens it either converges and focuses the light in a smaller area or it disperses the light beam spreading it out then the light passes through the lens its direction chan...

A lens is a transmissive optical device that focuses or disperses a light beam by refraction when the light beam passes through a lens it either converges and focuses the light in a smaller area or it disperses the light beam spreading it out then the light passes through the lens its direction changes because of refraction depending on the type of lens the light will either concrete on a smaller focus point or disperse lenses are used in many optical devices including glasses microscopes telescopes and cameras Concave lenses Aconcave lens is thicker at the sides that in the middle when light transmits through a lens refraction occurs and the angle the light middle when light transmits through a lens refraction occurs and the angle the lens travel changes the incident rays diverge as they move away from the normal line the image formed is a n upright and smaller sized version of the object therefore concave lenses are used to treat nearsightedness someone who is concave lenses are used to treat nearsightedness someone who is nearsighted can see objects nearby clearly but objects further away look blurry Rays from distant objects need to spread out before they reach the lens using concave lenses diverge the light rays allowing them to spread out before they enter the eye thai helps nearsighted people see they are further away to increase the refraction light thicker lenses are worn Convex lens A convex lens in thinner at the sides and thicker in the middle they work by refracting light inward towards a focal point convex lenses are used to correct farsighted vision where someone can ont see nearby objects clearly buy can see objects far away clearly convex lenses converge the incident ray towards the axis this means the ray bends towards teach other allowing them to meet on the other side of the lens that magnifies objects making them look larger a magnifying glass uses convex lenses to magnify an object eyeglasses with convex lenses solve long sightedness by bending the light ray that shortens the focal length and thus properly focusing the light ray on the retina microscopes also use convex lenses in fact modern microscopes use more than just a set of lenses they have objective lens that sit near the object and an ocular lens that sit closer to the user's eye using a system with more than one lens is called a round lens it allows for stronger magnification of 40x or more