• Reflection occurs when a wave reaches a boundary between two media, and some or all of the wave bounces back into the first medium.

Reflection can be total or partial. Think of examples of each.

Reflection can be total or partial. Think of examples of each.

• Partial reflection of light– About 2% of light’s energy is reflected from water

that strikes perpendicularly, the rest is transmitted.– About 4% is reflected from glass

• Total reflection of light (rigid to light waves)– Mirrors– Metals

Incident and reflected rays of light make equal angles with a line perpendicular to

the reflective surface.

What in the world does this mean?!?!What in the world does this mean?!?!

θincidence=θreflectionθincidence=θreflection

Incident light rayReflected lig

ht rayNormal

Angle of incidence Angle of reflection

θ θ

Reflective surface

Dejuan places a small, flat mirror flat against a wall. Standing close to the mirror, Dejuan could see his face from his eyebrows to his chin. Dejuan backed up five steps away from the mirror. Dejuan is now

farther away from the mirror. How much of his face will Dejuan see in the mirror this time?

• A) He will see more of his face.• B) He will see less of his face.• C) He will see the same amount of his face.

Mirror on the Wall

The dotted lines still hit the bottom of the mirror,

but their reflection misses the eye!

The dotted lines still hit the bottom of the mirror,

but their reflection misses the eye!

Virtual Image!Virtual Image!

• A real image is formed when the light comes from the object straight to your eye

• A virtual image is one which comes from a reflective surface and the object is not really located where you see it.

When you look at a flat mirror, where is your virtual image located?

When you look at a flat mirror, where is your virtual image located?

• If you wish to take a picture of your image while standing 2m in front of a plane mirror, for what distance should you set your camera to provide sharpest focus?

• What can you tell me about the frequency of light incident upon a flat mirror compared to the frequency of light reflected from the mirror?– What is your evidence???

• Why is it easier to see your reflection in glass when it is dark on the other side???

Your image appears as far behind the mirror as you are in front!!!

Your image appears as far behind the mirror as you are in front!!!

• If the differences in elevation in a surface are smaller than 1/8th the wavelength of the incident light, then the surface is considered to be polished.

• What is polished for one wavelength may not be polished for others.

• Could visible light be reflected from wire mesh? What about radio waves?

Of SoundOf Sound

• Sound reflection follows the same rules as light.• An ECHO is a reflected sound• In locations where walls are too reflective,

multiple reflections called REVERBERATIONS cause sounds to become garbled.

• The study of sound reflections is called ACOUSTICS.

Why are the walls in panels at the Radio City Music Hall?

Diffused sound reflection allows an audience member to hear large amount of sound from one spot instead of soft sound from many parts of the

wall.