Unit 8: Light and Optics Chapter 22: Optics 22.2 Refraction

SWBAT… describe causes of refraction. OBJECTIVE SWBAT… describe causes of refraction.

Refraction (#1) A straw in a glass of water makes a good example of refraction – the bending of light as they cross a boundary from one materials to another. Examples are optical devices, such as telescopes, binoculars, and fiber optics technology

Refraction (#2 and 3) index of refraction - measures the ability to bend light. Higher index of refraction = bend light by a large angle. Glass is higher that water

Refraction (#4 and 5) index of refraction -diamond has an index of refraction of 2.42. Diamond sparkle because of their high index of refraction. The “broken straw” illusion described above happens because the index of refraction of water and air are different

What direction does bend light? (# 6 & 7) The angle of refraction is the angle between the refracted ray and the normal line. A light ray going from a low index of refraction into a higher index bends toward the normal line. A light ray going from a high index of refraction to a low index bends away from the normal line.

Total internal reflection (8 and 9) The angle of incidence at which light begins reflecting back into a refractive material (90 degrees) is called the critical angle . Total internal reflection happens when the angle of refraction becomes greater than the critical angle (more than 90 degrees).

thin glass fibers that use total internal reflection to carry light Fiber optics (#10)

Prisms (#10 + 11) A glass prism splits white light into its spectrum of colors because each color is bent slightly differently. Colors: ROY – G - BIV

Dispersion (#13 +14) The variation in refractive index with color is called dispersion. Tiny rain droplets act as prisms separating the colors in the white light rays from the sun. Yellow is the color that refractive index values are based on.

Refraction Vegetable oil and glass have almost the same index of refraction. If you put a glass rod into a glass cup containing vegetable oil, the rod disappears because light is NOT refracted!

22.2 Investigation: Refraction Key Question: How do we describe the refraction of light? Objectives: Listen to beats and explain how the presence of beats is evidence that sound is a wave. Create interference of sound waves and explain how the interference is evidence for the wave nature of sound.