Light and Optics Physical Science 92 B Reference: Ch 14 & 15

Light We see objects because of their reflected light. Can carry heat Travels far and fast Travels in a straight line unless bent or reflected. Can carry color.

What makes light? Almost everything that creates light is made of atoms. Elements have electrons which are in shells. The further from the nucleus, the more energy it has. As it falls to a lower level, emits energy.

Visible Light and UV ROY G. BIV-colors of visible light. Sunlight emits UV along with other rays. Gives us Vitamin D Too much harmful. Most filtered by ozone.

Speed of Light Speed of sound-340 m/s Speed of light-300 million m/s Einstein figured out how light behaved Polarization Rays are all vibrating on the same plane. A polarizer allows only 1 type through. Ex: sunglasses. Many things use polarized light-laptop monitors

Color Color has freq and wavelength One goes up, the other goes down. Red-longest wavelength, lowest freq Violet-shortest wavelength, highest freq

How do I see color? Photochemical receptors receive the light (rods and cones) They release a chemical signal to the brain. Brain interprets the signal Rods-brightness, cones-the color Primary colors of light: red, blue, green mix together to make white. Additive and subtractive Primary colors of light are additive-each one adds more light and the result is white. Primary pigment colors are subtractive-each one takes away more light and the result is black. (magenta, cyan, yellow)

Optics and Reflection Optics-the study of how light behaves Deals with the collection and use of light to create images Includes: lenses, mirrors, and prisms Law of reflection: determines the reflected ray Light rays bounce off a mirror at the same angle at which they arrive We always define angles relative to the normal (the line perpendicular to the mirror (or lens)

Mirrors & Prisms Mirrors reflect light –Flat mirrors show true-size –Curved mirrors cause light to come together or spread apart Prisms cause light to change directions –Traditionally used to separate the colors of light and to show how light bends

Images Objects are any real physical things that gives off or reflects light Images are “pictures” of objects formed where light rays from the object meet Normally light travels in straight lines To make images, sometimes light must be bent between an object and your eye

Reflection & Mirrors A mirror reflects rays of light so that they change their path Mirrors create a virtual image –Image appears behind the mirror and is reversed –The light rays are reflected back to your eye at an equal but opposite angle Incident ray – the ray that comes from the object and hits the mirror Reflected ray – the ray that bounces off the mirror

Refraction and Lenses A lens uses refraction to cause light to come together or spread apart Refraction – The bending of light that occurs when light crosses a boundary between two different substances –EX. Glass, Plastic, Water Lens – a shape of transparent material that is used to bend the light rays –Shape is determined by how strong we bend the light