Answer:
1.A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.
2. A lens forms an image by refracting light rays. Light rays reflected from an object are refracted when they enter the lens and again when they leave the lens. They meet to form the image.
3. A cameras, microscopes, and telescopes. Ray diagrams show the types of images formed by convex and concave lenses.
