It’s a Rainbow Kinda World!!

Prisms

• Prisms break white light into a rainbow by refraction. Light goes in at an angle and bends.

• Different frequencies (of which white light is made) bend at different angles. So, the colors of light fan out.

Prism and different wavelengths (or frequencies):

Here are the average wavelengths of the rainbow colors of light

Red 650 nmOrange590 nmYellow 570 nmGreen 510 nm

Blue 475 nmIndigo 445 nmViolet 400 nm

A nanometer = 1/billionth of a meter

• Different frequencies of light we can see, give us the different colors of the visible light spectrum. Together they make white light.

ROY G. BIV

Lasers…are made of only one frequency of light in which all the waves are “in step”.

White light, red laser, blue laser

When light meets a barrier it can be….

• transmitted (go through)• absorbed (stay in it)• reflected (bounce off it)

Objects that…

• transmit most of the light are transparent• scatter light as it passes through are

translucent• reflect or absorb most of the light are opaque

When white light strikes an object

All the frequencies of light (ROY G BIV) are absorbed, except for the one that bounces back to your eye.

This red car appears red to you because the car absorbs OY G BIV, and reflects the R back to your eye.

• This black bowling ball absorbs all the colors and none are reflected to your eye. Black is the ABSENCE of light coming to the eye.

• The white bowling pins absorb none of the light and all the colors are reflected back to your eye. White is all the colors of light combined.

Shining colored light: if red, the apple can reflect red, with green or blue light, there is no red to reflect!

Your turn…

1. Figure out what happens when the primary colors of light are mixed in different combinations.

2. What happens when primary light is shined on your rainbow?

Materials: flashlights, color paddles, cellophane, rubber bands or anything else you can think of.

In your composition book

• Design a lab to answer the previous questions.PurposePredictionMaterialsProcedureObservations (lends itself to a chart)Conclusion

Mixing light

red

greenblue

magenta

cyan

yellowwhite

Primary colors:BlueGreenRed

Secondary colors:MagentaYellowCyan

How we seeLight enters through the cornea and then the pupil, with the iris controlling the amount of light.

It goes through the lens, inverting the image.

(Hopefully) it falls directly on the retina.

The retina’s photoreceptor cells are stimulated by the frequencies of light.

Finding your blind spotWhat creates it?

X

The “X” should be about 5 cm away. Cover your left eye and put the card at arm’s length with the dot in front of your right eye. Stare at the dot and bring the card toward you until the “X” disappears.

Correcting vision problems

Peripheral Vision

P

O

E

X

How we seeLight enters through the cornea and then the pupil, with the iris controlling the amount of light.

It goes through the lens, inverting the image.

(Hopefully) it falls directly on the retina.

The retina’s photoreceptor cells are stimulated by the different wavelengths of light.

Seeing color and light and darkCones respond to color:Red conesBlue conesGreen cones

Rods respond to:Light and dark

Combinations of these receptors help us to see all the different colors.

Why do objects appear only in gray tones in low light situations?

The three kinds of cones respond to these frequencies:

According to this graphic, why do we make tennis balls chartreuse (yellow-green)?

Color blindness: How do you suppose it happens?

The test to the left is simple.The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.About 12-20% of white males are colorblind.

How about some optical illusions, just for fun?!

Stare at the dot up top for 30 seconds. Then look at the lower dot. This is called an after image.

Stare at the center of the flag and for 1 minute and then look at a white sheet of paper.

(physiological illusion: after image)

Count the black dots!

(a physiological illusion)

How many colors do you see?

There are only 3 colors: White, green, and pink.There seem to be two different shades of pink,but there is only one pink. (Cognitive illusion: color constancy)

Free powerpoint template: www.brainybetty.com 31

Test what happens when you mix pigments

• What colors do you seem to get mixing the various primary colors of pigments?

• Why would this be different than mixing light?

Mixing pigments

cyan

yellow

magenta

blue

green

red

black

With filters: since the filters are transparent they only transmit their own color. The red reflecting from the apple cannot “get through” the green or blue filter.

Behaviors of Waves

• Refraction• Reflection• Diffraction • Interference• Absorption

What can you tell me about these?

Refraction

Bending of light waves as it goes in at an angle and changes speed going from one medium to another.

Lenses are based on this.

2 Common Lenses

Convex lens

ReflectionLaw of Reflection:

angle of incidence = angle of reflection

Regular reflection Diffuse reflection

Kinds of Mirrors

• Plane mirrors

• Concave mirrors

• Convex mirrors

So, waves can be reflected, transmitted (sometimes refracted), and……

AbsorptionWaves enter an object, but do not exit.Energy of the wave is transferred to the particles in the object and transformed into thermal energy.Example: a hot dog solar cooker

Diffraction Here are some water waves passing…

through a slitImage from upscale.utoronto.ca

around an object or end of a barrierImage from thestargarden.co.uk

InterferenceInterference resulting from diffractionImage from astro-canada.ca

Constructive interferenceImage from astro-canada.ca

The end