Ch. 19 - Light

III. Wave Properties of Light(p.546-550)

ReflectionRefractionDiffraction Interference

A. Reflection

Reflectionwhen a wave

strikes an object and bounces off

incident beam reflected beam

Normal

A. Reflection

Law of Reflectionthe angle of

incidence equals the angle of reflection

B. Refraction

Refractionbending of waves when passing

from one medium to anothercaused by a change in speed

• slower (more dense) light bends toward the normal

SLOWER

FASTER

• faster (less dense) light bends away from the normal

B. Refraction

Refraction depends on…

speed of light in the medium

wavelength of the light - shorter wavelengths (blue)bend more

B. Refraction

Example:

View explanation.

C. Diffraction

Diffraction

bending of waves around a barrier

longer wavelengths (red) bend more - opposite of refraction

D. Interference

Interferenceconstructive brighter lightdestructive dimmer light

E. Cool Applications!

Fiber OpticsTotal Internal Reflection

• when all light is reflected back into the denser medium

E. Cool Applications!

The “Broken Pencil”refraction

View animation and explanation of the “Broken Pencil.”

E. Cool Applications!

Rainbowsrefraction-reflection-refraction

E. Cool Applications!

Diffraction Gratingsglass or plastic made up

of many tiny parallel slitsmay also be reflectivespectroscopes, reflective

rainbow stickers, CD surfaces

E. Cool Applications!

Thin Films - Bubbles & Oil Slicksinterference results from double reflection

E. Cool Applications!

Blue Sky & Red Sunsets

NOON• less atmosphere• less scattering• blue sky, yellow sun

SUNSET• more atmosphere• more scattering• orange-red sky & sun

• Molecules in atmosphere scatter light rays.

• Shorter wavelengths (blue, violet) are scattered more easily.