Lenses

• Lenses are precisely shaped pieces of glass that have been developed and used in corrective glasses, telescopes, microscopes, binoculars, and magnifying glasses.
• Convex lenses are objects or shapes that curve or bulge outwards, like a circle or sphere.
• Concave lenses are objects or shapes that curve inwards, rather than bulging outwards.
• The principal focus of a lens is where light rays appear to converge or to diverge from.
• In a ray diagram, a convex lens is drawn as a vertical line with outward facing arrows to indicate the shape of the lens.
• The focal length of a lens is the distance between the centre of the lens and the focal point.
• Concave lenses are thinner in the middle than they are at the edges, causing parallel rays to diverge.
• In a ray diagram, a concave lens is drawn as a vertical line with inward facing arrows to indicate the shape of the lens.
• The distance from the lens to the principal focus is called the focal length.
• from the lens, the image formed by a convex lens is upright and magnified.
• Lenses are precisely shaped pieces of glass that have been developed and used in corrective glasses, telescopes, microscopes, binoculars, and magnifying glasses.
• The images formed by a lens can be upright or inverted, magnified or diminished, real or virtual.
• Magnification is the process of making an image larger or smaller than the object.
• Convex and concave lenses are used in magnification.
• Rays from a light source further from the principal axis will result in a smaller image than the object.
• Rays from a light source will appear to come from the same side of the principal axis, meaning the image will be upright.
• A real image is an image that can be projected onto a screen.
• A virtual image appears to come from behind the lens.
• A ray diagram is a diagram that represents the direction and angle of travel of light.
• To draw a ray diagram, draw a ray from the object to the lens that is parallel to the principal axis.
• Once through the lens, the ray should pass through the principal focus.
• A ray which passes from the object through the centre of the lens is also represented in some ray diagrams.
• Some ray diagrams may also show a third ray.
• Convex lenses are objects or shapes that curve or bulge outwards, like a circle or sphere.
• The type of image formed by a convex lens depends on the lens used and the distance from the object to the lens.
• Magnification is the ratio of the image height to the object height when using lenses.
• Cameras and eyes contain convex lenses.
• Peep holes are set into doors so the occupant can identify a visitor before opening the door.
• Lenses and curved mirrors can produce magnified images.
• Ray diagram for an object placed less than one focal length from a convex lens.
• Film must be loaded into the projector upside down so the projected image is the right way up.
• This works when the object is placed at a distance less than the focal length.
• Only the person using the magnifying glass can see the image.
• A magnifying glass is a convex lens used to make an object appear much larger than it actually is.
• Concave lenses always produce images that are upright diminished virtual.
• When a light ray splits up or spreads out on the other side of the lens, it is deflected from a straight path.
• In a film or data projector, this image is formed on a screen.
• For an object viewed through a concave lens, light rays from the top of the object will be refracted close refracted.
• Projectors contain convex lenses.
• For a distant object that is placed more than twice the focal length from the lens, the image formed by a convex lens is upright and magnified.