Notes

Outline

Technical Physics 2 Refraction

Refraction Refraction is the bending of a light ray as it passes obliquely (other than 90°) from one medium into another. Refraction is due to the changing speed of light from one medium to another. This is determined by the optical density of the material.

Index of refraction How much the light ray bends is dependent on the relative speed of the light in each substance. The index of refraction is a ratio of the speed of light in air (c) to the speed of light in the substance (v).

Laws of Refraction incident ray, refracted ray and normal are all in the same plane (2 dimensional) refracted rays are reversible

Snell’s Law The ratio of the sine of the angles is equal to the ratio of the velocity of light this can also be written

Snell’s Law (cont.) Changes in speed also result in changes in wavelength. Any part of the equation may be used.

Internal Reflection Total internal reflection occurs when light enters a less dense material at the critical angle qc. The refracted angle will be 90°

Apparent depth due to refraction, an object submerged in a more dense material will appear to be at a shallower depth than actual.

Other observations  Dispersion - separation of light into its component wavelengths. This produces the spectrum of color. Mirages - refraction in the atmosphere due to different densities of air. (warm vs cold)