Refraction and Lenses
Dec 27, 2015
Refraction and Lenses
Refraction• The change in direction or ‘bending’ of light.
Snell’s Law• Snell came up with a way to figure out how far light will ‘bend’
depending upon the medium the light traveled from and to.
Link to interactive Snell’s Law AppletWillebrord van Roijen Snell
1580-1626
Snell’s Actual Law
n1 is the index of refraction for the incident medium.
n2 is the index of refraction for the refracting medium.
θ1 is the incident angle
θ2 is the angle of refraction
Link to Überdork’s ridiculous tribute to Snell’s law.
Example Problem 1• A light beam in air hits a smooth lake at an angle of 30
degrees. At what angle is it refracted?
Index of Refraction and the Speed of Light
n = index of refraction
c = 3x108 m/s
Vmaterial = Velocity of light in that material
mediumV
cn
Total Internal Reflection• Total internal reflection is a phenomenon that happens only
when light passes from a more optically dense medium to a less dense optical medium. The incident ray’s angle is so ‘great’ that there is no refracted ray.
Link to Total Internal Reflection Animation
Applications of Total Internal Reflection
• Mirages
• Fiber Optics
• Diamonds
Turn yourself into a diamond
Example Problem 5• Find the critical angle for diamond.
Example Problem 6• The critical angle for a special glass in air is 41 deg.
What is the critical angle if the glass is immersed in water?
Dispersion of Light• The separation of light into it’s spectrum is called dispersion.
Lenses• Lens: Any transparent material with an index of refraction
greater than that of air which re-directs lights path
Lens Equations
Convex Lens Anatomy
Convex Example Problem
Concave Lens Anatomy
Chromatic AberrationChromatic Aberration – A defect where different colors are focused at different spots, especially at edges. Objects appear to be ringed in color.
Lens Applications
Nearsighted / Farsighted
Cameras