Light

OBJECTIVES

How light is made and how it travels.

How we see things

The difference between opaque, transparent and translucent materials.

Light

Light is a form of ______ENERGY

We need light to see things.

Objects that create light are ________ of light or LUMINOUS sources.

We see non-luminous objects because light bounces off them and enters our _____

SOURCES

EYES

Look at the picture – how does light travel?

Light travels in __________ lines.

We can draw light ray diagrams to show how we see things.

STRAIGHT

Draw lines (using a ruler) to show how the Scientist can see the test tube.

Draw lines (using a ruler) to show how the Scientist can see the test tube.

_________ are made because light cannot travel through some objects. Light cannot bend around them either.

SHADOWS

Things that light cannot travel through are called OPAQUE.

Light can travel through TRANSPARENT objects like glass.

Sometimes you can only see a glow of light through something. Materials like this are TRANSLUCENT.

Name two things that are OPAQUE.

Name two things that are TRANSPARENT.

Name one thing that is TRANSLUCENT.

Reflection, Absorption, and Refraction of Light

Vocabulary:

reflection, absorption, transmit, refraction

When Light Strikes an Object

• Light travels in a straight line.

• It will continue moving in a straight line, until it hit something.

• Depending on what it hits, light may behave in very different ways.

Reflection

• When light bounces off a surface, it is called reflection.

• When light is reflected it travels in a straight line away from the reflecting surface.

• Example of Reflection:

http://www.openschool.bc.ca/elementary/science4/html/bouncingLight.htm

Absorption

• Any time light hits a surface, some of it is absorbed, or taken in.

• When light is absorbed into a surface it is transformed from light energy, into heat energy.

• That is why on a sunny day it is cooler to wear a white t-shirt, than a black t-shirt; dark surfaces absorb more light than lighter surfaces.

Refraction

• Some materials transmit light, or allow light to pass through them.

• These transparent materials cause light to bend as it is passing through the surface.

• When the light bends, it makes things look like they do not match up.

Things to think about…

1. Which colour absorbs the most light?2. When light bounces off a surface, what is it

called?3. Describe what happens to light when it

passes through glass or water.4. What happens to a material when it absorbs

light?5. On a summer day, why is blacktop so much

hotter than the dirt next to it?