Physics Chapter 14 Study Guide
Refraction

Christiaan Huygen (1629 - 1695) - Dutch mathematician, astronomer, and physicist

Refraction

Refraction – the bending of a wave front as the wave front passes between two substances in which the speed of the wave differs or the bending of a wave disturbance as it passes at an angle from one medium into another

Some examples of refraction

Java Applet for Refraction

Why does refraction happen?

Law of Refraction

Index of Refraction – the ratio of the speed of light in a vacuum to the speed of light in a given transparent medium.

Indices of Refraction for Various Substances

 Solids at 20˚C n Liquids at 20˚C n Cubic zirconia 2.20 Benzene 1.501 Diamond 2.419 Carbon disulfide 1.628 Fluorite 1.434 Carbon tetrachloride 1.461 Fused quartz 1.458 Ethyl alcohol 1.361 Glass, crown 1.52 Glycerine 1.473 Glass, flint 1.66 Water 1.333 Ice (at 0˚C) 1.309 Polystyrene 1.49 Gases at 0˚C, 1 atm n Sodium chloride 1.544 Air 1.000293 Zircon 1.923 Carbon dioxide 1.000450

Applications of Refraction

Snell's Law

Snell's Law

Example 1

A light beam in air hits a sheet of crown glass at an angle of 30.0˚. At what angle is the light beam refracted?

Example 2

A laser beam in air is incident upon ethanol at an angle of incidence of 37.0˚. What is the angle of refraction?

Example 3

A block of unknown material is submerged in water. Light in the water is incident on the block at an angle of incidence of 31˚. The angle of refraction of the light in the block is 27˚. What is the index of refraction of the material of the block?

Thin Lens

Lens – a transparent object that refracts light rays, causing them to converge or diverge to create an image

Ray Diagrams for Lenses

Convex Lenses

Concave Lenses

Thin Lens Equation

Magnification Equation

Example 4

An object is placed 32.0 cm from a convex lens that has a focal length of 8.0 cm.

a. Where is the image?

b. If the object is 3.0 cm high, how tall is the image?

c. What is the orientation of the image?

Corrective Lenses for Nearsightedness

Corrective Lenses for Farsightedness

Combination of Thin Lenses

Compound Microscopes

Refracting Telescopes

Example 5

Two converging lenses are placed 20.0 cm apart, as shown in the figure. If the first lens has a focal length of 10.0 cm and the second has a focal length of 20.0 cm, locate the final image formed of an object 30.0 cm in front of the first lens. Find the magnification of the system.

Optical Phenomenon

Total Internal Reflection

Total Internal Reflection–the complete reflection of light at the boundary of two transparent media; this effect occurs when the angle of incidence exceeds the critical angle.

Critical Angle–the minimum angle of incidence for which total internal reflection occurs

Calculating a Critical Angle

Example 6

What is the critical angle for light emerging from carbon disulide into air?

Example 7

One method of determining the refractive index of a transparent solid is to measure the critical angle when the solid is in air. If the critical angle is found to be 40.5˚, what is the index of refraction of the solid?

Application of Internal Reflection

Dispersion

Dispersion–the process of separating polychromatic light into its component wavelength

Rainbows

Double Rainbow

Mirages

Chromatic Aberration

Chromatic Aberration–the focusing of different colors of light at different distances behind a lens