Applications of Refraction Answers to burning questions

Refraction Where do we see evidence of refraction? What use is refraction to us? Who cares?

Refraction in Nature

Rainbows Entering raindrop, white light separates into wavelengths because red light is refracted by a lesser angle than blue light Leaving raindrop, red rays have bent through a smaller angle than blue rays

Rainbows

Shimmering Light is refracted as it passes through air of different temperatures Air is warmest just above water; cools as you rise Light travels more slowly through colder air Total Internal Reflection (T.I.R.) occurs in lowest air layer

Shimmering That’s why you can see multiple reflections of the sun and moon in the water

Mirage Appears that water is on the road up ahead – always disappears! Happens when light travels from cool into warmer air Light bends farther from normal in warmest air T.I.R. occurs just above asphalt Pool of water is virtual image of the sky

Refraction Technology

Fibre Optics Light transmits info. along glass cable Cable must have small critical angle so light does not escape Used in sci-fi movies to represent tiny windows in giant spacecraft Used in medical technology (endoscopes)

Retroreflectors Return light back to its source in same direction Found naturally in vertebrate eyes Made with 2 or more perpendicular mirrors (corner cube) Makes road signs visible at night

Retroreflectors

Invisibility Cloaks?

We have the technology… YouTube videos “Notebook: Invisibility Cloak” (CBS) “Invisibility” “Invisibility Cloak”