Reflection

• The law of reflection states that the angle of incidence is equal to the angle of reflection.

• All angles are taken from the normal line not the surface!

Regular Reflection

• If all the normal lines are parallel to each other you get a precise image.

ReflectionThe image of a reflection is virtual, erect, and backwards.

Drawing a reflection.

Why is the front of an ambulance written backwards?

Convex and Concave Images

• A convex mirror will give you an upright virtual and smaller image.

• A concave mirror will give you a real inverted image if you are beyond its focal point.

Diffuse Reflection

• In Diffuse reflection you are not able to see a clear image because the normal lines are not parallel to each other. Example: white paper light is reflected but not like a mirror.

Reflection and Diffuse Reflection Explained.

The Law of Reflection states: The angle of incidence is equal to the angle of reflection.

http://ny.pbslearningmedia.org/resource/lsps07.sci.phys.energy.lightreflect/light-and-the-law-of-reflection/

Click on the above link:

Refraction

• The bending of a wave as wave enters a new medium.• A medium is what the wave is in. ie. Water, air, metal…• n1 sinθ1 = n2 sin θ2

Refraction and Critical Angle.

n = index of refraction

• The index of refraction is a ratio to the speed of light in a vacuum vs. speed of light in a substance. I like to think of it as optical density!

• Air is 1.00

• Water is 1.33

• Lucite is 1.5

• Diamond is 2.42

Calculate the speed of light in a substance.

• n = c/v

• c is speed of light (3.0 x 108 m/s)

• Find the speed of light in water.

• n = c/v

• 1.33 = (3.0 x 108 m/s) / v

• v = 2.256 x 108 m/s

The straw seems to be broken, due to refraction of light as it emerges into the air.

Diagram of refraction of water waves.

The source wave is encountering an area of decreased water depth.

Notice how the bottom of the wave is moving slower than the top.

Hence, you notice the bend.

Refraction

• As a wave enters a new medium with a larger index of refraction the wave slows down, the angle decreases and the wavelength gets smaller.

• The frequency of the wave does not change!

Internal Reflection

• Sinθc = 1/n

• The critical angle is the angle

of incidence where it causes

the light to be reflected at 90

degree to the normal . If the

angle of incidence is greater

than the critical angle you

get total internal reflection.

ie. fiber optics.