Light and Color for the Middle School

By Greg Corder

TOC1. Reflection and mirrors2. Refraction and lenses3. Applications of lenses and mirrors4. Color: light, pigments, and wavelength5. Diffraction6. Interference7. Light the electromagnetic wave8. Photoelectric effect9. Nature of light: particle, wave, or both?

The Law of Reflection

Flat surfaces reflect best.

Curved Mirrors

• Concave mirrors converge light.

• Convex mirrors diverge light.

Concave MirrorLight converges. This means that it comes together.

Also, the image is flipped past the focal point.

Convex MirrorsLight diverges. This means that light spreads

out.

Curved Lenses

• Convex lenses converge light. The image is flipped past the focal point.

• Concave lenses diverge light.

Refractions causes light to bend.

The shape of the lens determines how the

light behaves.

Applications of lenses and mirrors

Periscope

                                                                                            

Color

Dispersion…

Color separates using a prism because different colors have different wavelengths.

Red light bends the least and purple light bends the most.

Color depends on Wavelength of Light.

Colored lights combine to appear white.

Colored lights add to become white.Why then do paints add

to become black?

Answer: paints are pigments.

Pigments are chemicals which arecapable of absorbing one

or more frequency of white light.

Behaviors of light

Diffraction – a wave bends around an objectLight is a wave!

Light through a small slit.

Interference: light is a wave!

Polarized light is a

wave!

The Electromagnetic Spectrum

•

Maxwell - (c. 1864) light is an EM wave

The photoelectric effect: light is a particle!

The puzzle of intensity vs. energy

                                                      

Einstein - (1905)–The duality theory of light–Light has a dual nature: light is both a

particle and wave

Sources:http://www.glenbrook.k12.il.us/gbssci/phys/Class/BBoard.htmlhttp://www.mhhe.com/tilleryTillery, Physical Science.http://cougar.slvhs.slv.k12.ca.us/~pboomer/physicslectures/secondsemester/telescopes/refracting.jpg