Light comes in discreet packages called photons.
Light has properties of a particle and wave, known as the dual nature of light.
Similarities of Light to Sound Source determines the frequency. Speed depends on what it is traveling through. Light travels fastest in a vacuum, slowest through water. v = f λ still applies. The speed of light in a vacuum is constant and represented by c. c = f λc = 3.00 ˣ 10 8 m/s
The primary colors of light are red, green, and blue.
The secondary colors of light are yellow, cyan, and magenta.
Notice the refracted ray is smaller than the incident ray.
This is because light is slower in water than in air!
Facts about Refraction When light goes from a faster to slower medium, it will bend towards the normal. The Angle of Refraction is always dependent on the Angle of Incidence!!! The higher the Index of Refraction the slower light travels through the medium!!
Total Internal Reflection This occurs because an incident beam enters a medium with a lower index of refraction, such as from water to air. (Light is refracted away from the normal) The critical angle (θ c ) is reached when the light is refracted at 90° and travels along the surface. At angles greater than the critical angle (θ c ) total internal reflection occurs.
Notice Total Internal Reflection only occurs when the angle of the Incident beam is greater than the critical angle. θ i ˃ θ c
Summary of Requirements for Total Internal Reflection Index of Refraction must be lower for medium incident beam in entering. n i ˂ n r or n 1 ˂ n 2 The angle of incidence must be greater than the critical angle! θ i ˃ θ c or θ 1 ˃ θ c
Calculating Critical Angle n1n1 n2n2 sin θ c = n 1 is the index of refraction for the medium where the incident beam originated n 2 is the index of refraction for the medium the incident beam enters
From Water to Air n1n1 n2n2 sin θ c == 1.00 1.33 sin θ c = 0.7518 sin -1 θc θc =(0.7518) θc θc = 48.8°
If a light source is 5 m underwater, how far away on the surface will total internal reflection occur?? Air n = 1.00 Water n = 1.33 y = 5 m x = ? m
Air n = 1.00 Water n = 1.33 y = 5 m x = ? m tan 48.8° = y x = 5 m x x= tan 48.8° x=5.71 m
Dispersion of Light Different colors of light have different indexes of refraction. This causes the “rainbow effect” under the proper conditions. For some media, such as air, this difference is miniscule and rarely noticed. For glass the difference in indexes of refraction can be profound for each color of light.
Indexes of Refraction for a piece of glass. Red1.502 Orange1.506 Yellow1.511 Green1.517 Blue1.523 Violet1.530
θ 1 = 60° We make use that the sum of the angles in a triangle are always 180° θ2 θ2 θ3 θ3 θ4 θ4