Lesson 29 Wave Characteristics of Light

Wave Function for Light v=λν i.For light v = 3.0x108m/s according to Einstein (maybe false now????)

Example I Determine the frequency of red laser light with a wavelength of 633nm

Answer 4.7x10 14 Hz.

Remember Light can Reflect Refract (bend) Be absorbed θ i = θ r

Refraction When light enters a new medium three changes may occur. The speed and wavelength will always change. The direction may change called Refraction. The speed of the light slows down and bends towards the normal.

Refraction The ratio of speed of light in a vacuum (c) to a given medium (v) is called the index of refraction (n) n = c/v……extremely important Can be considered a measure of the mediums optical density

Refraction If light enters a transparent substance at an angle to the surface (other than 90°) the light will bend. When the light exits the medium into an area of low optical density the light will bend away from the normal and speed up.

Example II Light enters 90° into a triangular piece of glass. Sketch the ray of light as it pass through the triangle and exits back into the air.

Answer

Example III A rectangular piece of glass(n = 1.50) is placed in a pool of water(n=1.33) and light is shone on it at an angle as illustrated. Sketch the ray as it enters and exits the glass.

Answer

Snell’s Law Quantitatively the angles can be calculated by using Snell’s Law n 1 sin θ 1 = n 2 sin θ 2 Where θ 1 and θ 2 are the angle of incidence and refraction.

Example IV Light strikes a flat surface of clear water at an angle of 35°. Sketch the refracted ray and determine the angle of refraction. (n air = 1 and n water = 1.33)

Answer 26°

Example V Find the angles of refraction when light enters glass (1.50) from water (1.33) at an angle of 20°.

Answer inside (18°) exit (20°)

Example VI Light with a wavelength of 500nm enters diamond from air. Determine the wavelength and frequency of the light while it is in diamond. (n diamond = 2.4, and frequency does not change ever)

Answer 210nm