1. The Refraction of Light SNC2P – Optics

2. Refraction Refraction: the bending or change in direction of light when it travels from one medium into another Refraction occurs because light travels at different speeds through different media

3. Rules for Refraction The Rules for Refraction 1.The incident ray, the refracted ray and the normal all lie in the same plane. The incident ray and the reflected ray are on opposite sides of the line that separates the two media. 2.Light bends toward the normal when the speed of light in the second medium is less than the speed of light in the first medium. Light bends away from the normal when the speed of light in the second medium is greater. Angle of Refraction: the angle between the refracted ray and the normal.

4. Total Internal Reflection When light travels from one medium into another, some of the light is reflected and some is refracted. Recall: Light bends away from the normal when it speeds up at the boundary of two media (example: as light travels from water to air) As angle of incidence increases, the angle of refraction increases The angle of incidence which results in the angle of refraction becoming 90 o is known as the critical angle If the angle of incidence increases past the critical angle the refracted ray will no longer exit the medium. Instead, it will reflect back into the medium. This is known as total internal reflection. Water has a critical angle of 48.8 o

5. Total Internal Reflection and the Critical Angle

6. Diamonds have a high index of refraction which means that they have a very small critical angle: 24.4 o A light ray can bounce around several times inside the diamond before eventually exiting through a top face of the gemstone This causes the “sparkling” effect Fibre optics is a technology that uses light to transmit information along a glass cable Information is transferred into light energy and enters one end of the optical fibre. Due to the small critical angle, internal reflection occurs along the length of the optical fibre until the light emerges at the end and is then decoded

7. Demo and Video Refraction

8. Homework Complete the worksheet and the questions on the handout.