Download Class notes on LIGHT

Class notes on LIGHT
•Light is a type of energy that is composed of 2 things:
–An electromagnetic wave
–photons
Light travels at a speed of 300 000 km/s in a straight line.
•Definition: a photon is a particle of light that is derived from energy emitted by an excited
electron returning to a lower energy shell.
•When light hits an object, 3 things can occur:
–Transparent object: light passes through the object and is seen on the other side.
–Translucid object: a portion of light goes through the object (other side is not visible).
–Opaque object: light does not go through (completely blocked).
Visible light corresponds to a series of rays found between red and violet.
Beyond red is infrared (invisible) and beyond violet is ultraviolet, also invisible, and can be
seen by insects.
Reflection: There is a change in the direction of the rays as it meets a surface.
Absorption: A portion of light rays can be absorbed by a susbtance while the rest is
reflected. (Earth absorbes sunlight and reflects the rest back to space).
Refraction: Light rays are bent when passing from one medium to another because of the
difference in the light’s speed in each medium. (Medium = air (faster) and water (slower)).
White light dispersion
•Thin ray of light is projected on a prism: the visible spectrum of white light appears.
Different wavelengths of white light are separated and appear on the other side of the
prism.
•White light is composed of all colors mixed together.
Bill Nye video watched in class: http://www.youtube.com/watch?v=gtgBHsSzCPE
Videoes not watched in class, but are helpful:
Video on dispersion of light: •http://www.youtube.com/watch?v=7Fl0GZsBhGo
Video on the electromagnetic spectrum: http://www.youtube.com/watch?v=cfXzwh3KadE