Lesson 3

Requires a flashlight, mylar square, index card and blocks.
Online mixing of the Primary Colors of Light.
Does light travel in a straight line? Does it ever travel in a curve, relatively speaking?
How is bouncing a ball similar to bouncing a beam of light? Reflections on reflections.

What did you do last time?

primary

yellow

magenta

cyan

secondary

rainbow

PRINT the word next
to the image on the next slide.

Video Play Button

Combining the Primary Colors of Light

Play the video below.

Move the red, green and blue circles around yourself.
What colors do you see when the circles of light overlap?

Video demonstration the mixing
light using red, green and blue LEDs.

javalab.org

Mixing the Primary Colors (RGB) of Light
to get the Secondary Colors.

Find a flashlight
and baby powder
OR flour.

In a darkened room,
sprinkle some powder
in front of the flashlight.

Do you see the beam of light?

What path does light take?
Is it zigzagged or curved or straight?

Light travels in a straight line!

Not convinced? Watch this video demonstration.

If an adult has
a laser pointer,
ask them to repeat
the experiment
on the last slide
using the laser.

Click on video to watch.

FUN: To be more precise, space is curved by very large celestial objects, and the path of light curves with space.

For most earthbound people, light travels in a straight line!

Showing that light travels
in a straight line!

Click to watch the video.

Though light travels in a straight line,
you can BOUNCE light like a BALL!

HOW DOES
a ball bounce?

angle-in

angle-out

equals

No matter how the ball hits the ground (red arrow),

it will bounce AWAY at the same angle (blue arrow).

Bounce a ball.
Watch its path.

Point a flashlight
at a mirror.

To where does the beam bounce?
Look for it on other walls.

Try different angles.
Can you control where the beam goes?

REFLECTION

The BOUNCING of light
off a surface is called

Let's reflect some light!
Find your light kit and a clean surface.

When you are ready, go to the next slide.

white
card

mylar
square

3 small blocks

flashlight

Find these items
around your home:

Cut a 2 inch (5 cm) slit in the white card.

Attach the mylar
to a block with tape
or a glue stick.

Use two blocks
to hold up the card.

Place the mylar
in front of the slit,
like this.

Place the flashlight on
a white piece of paper.

Tilt the light downward
until you see the line of white light on the white paper. Make the light BOUNCE off the mylar.

Is the path of the light beam
like the path of a ball?

Change the angle
of the mylar mirror.

The angle of the light going into the mylar mirror equals the angle going out.

Here is how to measure the angle of light,
coming in and bouncing out.

Bouncing light to make patterns.
Uses a laser pointer. Adult required.

This is a favorite classroom experiment. We did it using blocks and mylar mirrors.
Students designed their patterns. I tested each pattern with one laser pointer.
Students stood up during the laser test, so all eyes were safely out of range.