Science Starter: March 5, 2012Write out the definition and match the correct term in your science notebook.2) How a light wave bens when it enters a new medium at an angle3) How a light wave bounces back when it hits a barrier4) The type of wave visible light isElectromagnetic Wave RefractionReflection SpectrumMechanical Wave Radiation

Science Starter: March 6, 2012Write the question and correct answer in your science notebook4) An EM wave is caused by a disturbance in a. The atmosphere b. A material medium c. A field5) In a vacuum, the speed of EM waves a. Always remains constant b. Decreases as the waves spread out c. Depends on the source of the wave

Light Sources and Interactions

Facts about Visible Light Light is the only form of EM radiation for which humans have specialized sensory organ. The human eye is very sensitive to light and color Most living creatures depend on visible light for their survival.

Incandescence The Suns high temperature produces light of every wavelength. Incandescence- the production of light by materials at high temperatures Example: sun, lightening, fire, incandescent light bulbs

Living Things Produce Light Luminescence- the production of light without high temperatures Bioluminescence- the production of light by living organisms Light is created with a chemical process rather than intense heat

Human Technology Produces Light Incandescent Light Bulbs- uses a glass bulb and a tungsten filament Halogen Light Bulbs- used a quartz bulb, tungsten filament, and a halogen gas mixture Fluorescent Light Bulbs- uses phosphor coating, electrical current, mercury vapor and other gases.

Fluorescent and LED Lights Fluorescence- occurs when a material absorbs EM radiation of one wavelength and gives off EM radiation of another Light emitting diode (LED)- a semiconductor that converts electric energy directly into light Advantages of LED: produce brighter light, do not break, uses little energy and heat, can last for decades

Light Waves Interact with Materials Transmission- the passage of an EM wave through a medium Transparent- materials that allow most of the light that strikes to pass through Translucent- materials that transmit some light, but they also cause it to spread out in all directions Opaque- materials that do not allow any light to pass through

Light Waves Interact with Materials Absorption- the disappearance of an EM wave into the medium. Absorption affects how things look, because it limits the light available to be reflected or transmitted.

Light Waves Interact with Materials Scattering- the spreading out of light rays in all directions, because particles reflect and absorb the light.

Light Waves Interact with Materials Polarization- quality of light in which all of its waves vibrate in the same direction

Wavelengths Determine Color When all wavelengths of visible light are present the light will appear white. A prism is a tool that uses refraction to spread out the different wavelengths that make up white light.

Color Reflection and Absorption The color of an object or material is determine by the wavelength it absorbs and reflects.

Primary Colors of Light The human eye detects three color bands: red, green and blue. When all colors are mixed together you perceive white light