Refraction

Refraction

Refraction When light enters a new more dense medium A) speed decreases B) wavelength decreases C) direction changes if angle i ≠ 0 D) frequency remains the same

Refraction When light enters a new more dense medium The new direction is toward the normal and since light rays are reversible, When the ray enters a less dense medium the rays bend away from the normal.

Refraction in a Ripple Tank

From less dense to more dense

From more dense to less dense

I See You – You See Me Notice that the fish appears more shallow to the person.

Snell’s Law n1 sin θ1 = n2 sin θ2 n is the index of refraction and describes the optical density of the medium. The greater the index of refraction, the slower the speed of light. This is an inverse relationship Also

n1v1 = n2v2

n1λ1 = n2λ2

http://www.netzmedien.de/software/download/java/brechung

The Magic Elixir of Life What would happen if we smash a pyrex rod, n = 1.5 and put it into a beaker of oil, n = 1.5 ?

Index of Refraction Medium Vacuum

Index of refraction = n 1

Critical angle = θc  

Water

1.33

 

Lucite

1.5

 

diamond

2.4

 

Sunrise - Sunset Why on the equinox is a day 12 hours and 10 minutes and not just 12 hours?

Sunrise - Sunset

DEMO

Why is the Sky Blue? Scattering of Light The amount of scattering is inversely proportional to the cube of the wavelength. Blue has the shortest wavelength and therefore scatters the most. Red the least

Scattering of Light

Scattering of Light

Internal Reflection This occurs only when light travels from more dense to less dense media.

To ta l

Internal Reflection

Demonstration, Total Internal Reflection

Notice that light is not able to get out of the water at an angles greater than 42°

Total Internal Reflection The critical angle, θc n1 sin θ1 = n2 sin θ2 when θ 2 = 90 θ1 is the critical angle, θc and the formula becomes sin θc = 1/n http://freespace.virgin.net/gareth.james /virtual/Optics/Refraction/refraction.html

Index of Refraction Medium Vacuum

Index of refraction = n 1

Critical angle = θc  

Water

1.33

 

Lucite

1.5

 

diamond

2.4

 

Rainbow

Rainbow

Rainbow

Dispersion http://www.phy.ntnu.edu.tw /java/optics/prism_e.html

Mirages

Mirages

Looming

Towering Image Under Superior Mirage

Looming Superior Mirage

Towering Underscale is greatly exaggerated. Superior Mirage allows sight beyond Image the horizon: Superior Mirage