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.

1 What did you do last time? 2 primary yellow magenta cyan secondary rainbow PRINT the word next
to the image on the next slide.
L-Lesson 3 rai sec yel prim cya mag
4 Combining the Primary Colors of Light Play the video below. 5 A Video on Rainbows and the Primary and Secondary Colors of Light. 6 2 1 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?
7 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.
8 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! 9 Two students show that light travels in a straight line! 10 Though light travels in a straight line,
you can BOUNCE light like a BALL!
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.
11 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?
off a surface is called
13 Let's reflect some light!
Find your light kit and a clean surface.
When you are ready, go to the next slide.
14 Find these items in your kit: white
3 small blocks flashlight Find these items
around your home:
15 Cut a 2 inch (5 cm) slit in the white card. Attach the mylar
to a block with tape
or a glue stick.
1 2
16 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.
3 6 4 5 Tilt the light downward until you see
the line of white light on the white paper. Make the light BOUNCE off the mylar.
17 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.
18 Here is how to measure the angle of light,
coming in and bouncing out.
19 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.
Select Box to See Video
20 Lasers are used for surgery as well as
for high-precision, machine-controlled cutting.
Powerful lasers can be very dangerous.
They can damage your eyes and must be treated with respect.