Chapter – 16 Light

Electromagnetic radiation – energy carried through space in the form of waves.

EM Spectrum Over view of the EM Spectrum http://missionscience.nasa.gov/ems/emsVideo_01intro.html

LT #1 Quiz

What is Visible Light? electromagnetic radiation/waves with wavelengths between 400 nm and 700 nm that stimulates the retina of your eye. Nm = 1 x 10-9 m - 0.000000001 m A nanometer is tiny!!! The average human hair has a thickness of 80,000 nanometers!

Electromagnetic Spectrum (700 nm) (400 nm)

Electromagnetic waves do NOT need a medium. How fast light travels is dependent of the median in which it travels through. speed of light in a vacuum = 3.0 x 108 m/s

Problem Solving v=speed of light in a vacuum = 3 Problem Solving v=speed of light in a vacuum = 3.0 x 108 m/s v= d/t or v =frequency x wavelength

Problem Solving Example 1 It takes about 35 minutes for light to travel from the Earth to Jupiter. Determine the distance to Jupiter from Earth.

Problem Solving Example 2 Determine the frequency of yellow light which has a wavelength of 570 nm.

Problem Solving Example 3 WLUP broadcasts at a frequency of 97.9 kHz. What is the wavelength of these radio signals?

Nature of Light Light has a dual nature. It behaves like both a wave and a particle. Video on quantum physics Light exhibits the 4 wave behavior: Reflection Refraction Diffraction Interference

Visible light is a collection of all the colors of the rainbow which together make white light. Each color has its own wavelength and frequency but they all travel at the same speed (until they hit a medium).

Cyan, Magenta and Yellow. Primary Colors The three primary colors of light are: RED, GREEN, BLUE and the secondary colors of light are: Cyan, Magenta and Yellow.

When mixed

Colors by Addition When light is directly mixed, we see colors as it is and it is called colors by addition. Red + Green = Yellow Green + Blue = Cyan Blue + Red = Magenta AND RED + GREEN + BLUE = WHITE

Complementary Colors Any two colors added together that make white. Yellow is complementary to blue yellow = green + red then if you add blue you get white. Cyan and red magenta and green

LT #3

Colors By Subtraction Dye – a molecule that absorbs certain wavelengths of light and reflects others. Ex. a tomato is red because it reflects red light to our eyes.   Pigment - Like a dye but can be seen under a microscope, often it is a finely ground inorganic compound.

When light hits on a red object the object reflects red back and we see red. If red light shines on a blue object, which only reflects blue, we will see black because the object absorbed the red light.   When you shine a yellow light onto summer grass, what color will you see? green yellow light = red and green, the grass reflects green and absorbs red.

LT #4