Bending Light, Fiber Optics and Optical Phenomena in

NatureThe double rainbow!!!

Partial Reflection & Refraction

• Sometimes when you look out a window you see outside and you see your reflection at the same time

• This depends on the angle of incidence as well as the relative indices of refraction of the two media.

• Consider air to water: light traveling direction at the water (at 90º) will go straight through, however as the angle of incidence increase more light is reflected rather than passing straight through

Scuba diving• Because at large

angle of incidence most of the light is reflected off the water when you are scuba diving light appears to be coming through a hole above you at the surface of the water

Water and refraction

• Even though you know water is clear, you have difficulty seeing things farther away from you in the water.

• This is because when you look farther away you increase the angle of incidence which causes more reflection and blocks your view into the water.

Critical angle & Total Internal Reflection

• The angle of incidence that produces a refracted ray at an angle of 90º from the normal

• It has the symbol <c• When the angle of incidence is greater

than <c you get total internal reflection and all light is reflected back not passing through the medium.

Changing the direction of light• We can control light by putting the medium

borders at large angles of incidence so that we get total reflection.

• Bike reflectors and optical fibers are examples- with bike reflectors light will always bounce back the way it came

Fiber OpticsTotal internal reflection occurs all the way through the fibre so light travels quickly --telecommunications uses fiber optic cable to send information quickly--the medical field uses fiber optics in two ways, one to light up the area through endoscope (sending a tube into the body) second it uses fiber optics to send back images that the doctors can analyse. Non invasive

Rainbows and double rainbows

Sun dogs• Similar to rainbows,

but instead of water droplets it is ice crystals refracting sunlight.

• The most stunning sun dogs occur on cold clear mornings or evenings

Apparent depth

Shimmering and mirages

• Shimmering small scale• Mirage-large scale• Simmering is the apparent movement of objects

in hot air over objects and surfaces• Mirages are the bending of light rays passing

through layers of air that have extremely different temperatures. Since you are used to thinking that light travels in a straight line you interpret the origin of the light being on the ground when it is really the sunlight being refracted upwards.

Mirages

QuickTime™ and a decompressor

are needed to see this picture.

Homework

• Case study Pg 472 and 473

• Pg 475 # 1-7