Visible Light/Optics

Producing light without heat is called luminescence Visible light includes all the wavelengths of light the human eye can detect Most comes from the sun The sun glows with light because its so hot – incandescence Producing light without heat is called luminescence

Luminescence Fluorescence – substance absorbs shorter-wavelength UV light and gives off light in visible light Bioluminescence – production of light by living things as a result of chemical reactions

Artificial Light Sources Incandescent light bulb – phased out bulbs, get so hot they glow Fluorescent light bulbs – CFL’s, coating on inside of bulb absorbs UV radiation, then gives off energy as visible light Neon Light – electricity through a gas (yesterday) LED – light emitting diode – semiconductor that gives off visible light when electric current flows through it.

Visible Light and Matter Reflection – light bounces back from a surface that it can’t pass through If the surface is smooth like a mirror, reflected light forms a clear image – regular reflection If the surface is rough – image is not clear – diffuse reflection

Law of Reflection Angle of incidence = angle of reflection

Transmission Refraction – light is bent has it passes through a medium Scattering – light bumps into tiny particles of matter and spreads out in all directions

Absorption Light transfers energy to matter rather than being reflected or transmitted Added energy increases the temperature of matter

Mirror Glass with a shiny metal backing that reflects all the light that strikes it Mirrors may be flat or have curved surfaces Shape determines type of image formed

Plane mirror – the one in your bathroom – image is right side up, life sized Left and right are reversed Concave Mirrors Curved surface ))))))))) Car headlights and some telescopes

Convex Mirrors (((((( Can gather and reflect light from a wide area (side mirror on car)

Lens A lens is a transparent object with one or two curved surfaces Typically made of glass (or clear plastic) A lens refracts, or bends light to form an image

Concave Lens Its thicker on the edges, thinner in the middle. Causes light to diverge. Image is right side up and smaller

Convex Lens Causes light to converge. Forms image that can be larger or smaller depending on distance (think magnifying glass)