Optical Effects

Light and ColorIn Nature

The Blue SkyOxygen and Nitrogen molecules in the Air are the

right size to scatter blue light best.Thus if you look anywhere but at the Sun you see

the scattered, Blue Light.

The Red Sunset

The Sunset is red because the light passes through a great distance of air.

Blue and other colors are scattered away…Only Red is left in a large quantity.

RainbowsDrops of falling rain can act as a prism refracting the

colors of white light in different directions.They send out the violet rays at 42° from the direction

the light came in.(copy diagram)

Rainbows occur when there is both rain and sun.If you want to see a rainbow stand with the sun

behind you and rain in front.Look directly away from the sun (at the anti-solar

point).The rainbow is a circle that is 42° away from the ASP.Usually part of the circle is below the horizon and so

all you see is a “bow”

HalosHalos are an effect similar to Rainbows, but

caused by light refracting in ice crystalsThey form circles around the light source

Depth in Water

Refraction can make things appear where they are not

In water they will appear less deep than they are.

(copy diagram)

This is also why a straight stick stuck in water appears bent.

Total Internal Reflection

When light refracts because it speeds up the angle of refraction is larger than the angle of incidence

If the angle of incidence is large enough the light will be refracted back into the medium, it will be

“Totally internally reflected”Total Internal Reflection is used in optical

fibers to keep the light from leaving the fiber

Mirages

An Inferior Mirage Occurs when there is a layer of hot air near the ground.Light from the sky and objects in it is totally internally

reflected back up And thus appear to be on the ground!

A Superior MirageOccurs when there is a layer of cool air near the

ground.Light from the ground and objects on it is totally internally

reflected back down

and thus appear to be in

the sky!