Light

These are all LUMINOUS.

What are some sources of light?

What do luminous objects do?

LUMINOUS objects give off light.

Is this a luminous object?

No, neither the Moon nor a mirror is a source of light. They reflect light from other sources.

How does light travel?

Light travels straight and fast.

How fast does light travel?

Light travels at

300,000 kilometers per second.

How can we control light?

We can block it when it hits something OPAQUE. This makes a SHADOW.

What does OPAQUE mean?

Opaque means you can’t see through it.

shadow

How can we control light?

We can REFLECT it with a mirror.

What does REFLECT mean?

REFLECT means light bounces off it.

mirror

laser

How can we control light?

We can bend it when it pass through something TRANSPARENT .

What does TRANSPARENT mean?

Transparent means you can see through it.

How can we control light?

We can scatter it when it pass through something TRANSLUCENT .

What does TRANSLUCENT mean?

TRANSLUCENT means you can almost see through it.

How do we see things?

When light reflects off an object hits our eyes.

LAW OF REFLECTION

plane mirror

normal line

angle of incident

incident ray

angle of reflection

luminous object

refle

cted

ray

What happens when light hits smooth surface?

It follows the law of reflection.

What happens when light hits a rough surface?

It still follows the Law of Reflection but it scatters.

This is DIFFUSE reflection.

What happens when light hits a transparent surface?

It bends. This is called REFRACTION.

What happens a light ray hits this glass block?

The glass block is more dense than the air, so the light ray bends toward the normal line.

What happens a light ray leaves this glass block?

The air is less dense than the glass block, so the light ray bends away from the normal line.

Can you label the picture?

A

B B

C

D

A: Light ray

B: Normal Line

C: Angle of Incident

D: Angle of Refraction

What is a lens?

A lens is a transparent, curved object that refracts light.

What kinds of things have lenses?

Many objects in your daily life use or have lenses.

What are the two kinds of lenses?

They are convex lenses and concave lenses.

What happens when light hits a convex lens?

A convex lens causes light rays to focus (bend toward the normal line) .

What happens when light hits a concave lens?

A concave lens causes light rays to spread out (bend away from the normal line) .

THE END