Unit on Light

Presentation Created

by

Mr. Dabb

What do we need Sun light for?

• To see• For plant life• For animal life• To have weather• To heat the Earth• Petroleum Products: From prehistoric plants and

animals.• For Oxygen• Vitamin D (Through our skin)• Everything

Visible Light (Spectrum)

• Consists of the colors of the rainbow.– Red

– Orange

– Yellow

– Green

– Blue

– Indigo

– Violet

• The colors of the rainbow make a name.

• R

• O

• Y

• G

• B

• I

• V

Get it? Roy G. Biv?

When all the colors of visible light are mixed…

• We get white light.– This is different than mixing paint. If you mix all the colors

of paint, you will get black.

When Light Strikes an Object

• The light can be reflected.• The light can be absorbed. (Sucked in like

a sponge)– The light goes into the object.

• The light can be transmitted.– The light goes through the object.

• Many times it is a combination of all of the above.

Regular Reflection

• When parallel rays of light hit a flat and smooth surface, the reflection leaves at the same angle that it hits. This is the law of reflection.

When light hits a flat smooth surface at a certain angle…

It reflects off at the same angle.

Diffuse Reflection

• Happens when parallel rays of light hit a bumpy or uneven surface. The light reflects in all different directions because it hits the bumpy surface at different directions.

Opaque Objects

• Light cannot pass through (transmit through) an opaque object.

• Some light is reflected on opaque objects and some light is absorbed.– If an object is red, all the colors of the spectrum

are absorbed, except red, which is reflected.

How do we see white opaque objects?

• All the colors of the visible spectrum are being reflected.

How do we see black opaque objects?

• All the colors of the visible spectrum are being absorbed.

Transparent Objects

• Transmits light allowing it to pass through

• Allows almost all of the light to pass through an object. It looks clear.– glass– water– air

Translucent Objects( Almost SeeThrough Objects)

• Scatter light.– Some light is reflected, absorbed, or

transmitted.

• You can tell something is behind a translucent object, but your not sure what it is.

Mirrors

• Plane or flat mirrors– Like the mirror in your bathroom

• Concave mirrors– Mirrors that looked caved in.

• Convex mirrors.– Mirrors that are bowed outward

Mirrors

• Describe how a person will look in a concave mirror: Upside down.

• Describe how a person will look in a convex mirror: Wider and stretched out.

• Describe how a person will look in a flat mirror: Backwards or symmetrical image.

What are these different mirrors used for?

• Flat Mirrors:– Bathrooms– Dressing Rooms– Rear view car mirror– Places where you need to

see yourself.– Dentist Office

• Concave Mirrors– Fun houses– Spoons– Flashlights

• Convex Mirrors– Round car mirrors– Convenience Stores– Hospitals– Anywhere you need to see

around corners.– Fun Houses

Reflection vs. Refraction

• Reflection is when light bounces off of something.

• Refraction is light bending when it goes through a medium.– A medium is something that light could go

through.

Refraction

• Objects that go into water look broken because the light is refracting. That means the light is bending.

Lenses

• Lenses are different than mirrors because they refract light instead of reflect light.

• Remember!!– Lenses are transparent or clear.– Mirrors are opaque.

Lenses

• There are two basic types of lenses.– concave

– convex

Makes images smaller.

Makes images larger.

Eye Diagram

Diagram thanks to http://www.nei.nih.gov/health/eyediagram/