Monday, December 15, 2008

Record homework. Unpack. Get response pad. Permission slips on the stool.

AgendaAgenda: Quiz on 16.3 & 16.4 Completion of electromagnetic spectrum notes Light notes – LOTSLOTS of them!

Visible Light

The portion of the electromagnetic spectrum that our eyes can detect is called visible light. We’ve

developed tools and techniques to study visible light and to manipulate visible light to use for our benefit.

Let’s begin our visible journey….

Objects Interact with Light

I. When light strikes an object it can be:

A. Absorbed – opaqueopaque objects absorb light

B. Reflected – opaqueopaque objects reflect light

C. Transmitted by:

1. Transparent objects- all or most light passes right through allowing you to see what is on the other side

2. Translucent objects - some light passes through; cannot clearly see the objects

Light Interacts

Classify these 13 objects as either opaque, translucent, or transparent. Title three columns and write the name of each image in the correct

column.

Opaque Translucent transparent

No light (or nearly zero) passes through. It is all reflected or

absorbed.

Some light passes through the object.

Nearly all to all light passes through the object. “See through”

Review

I. When light passes through one type of matter (a _____________) to another, such as from gas through to liquid or a solid, it changes speed, which causes bending or a change in direction; this is called __________________.

II. Prism – ______________________ white light; each wavelength bends by a different amount so the seven named __________ become visible. These are (list in order from longest wavelength to the shortest):

III. Rainbows – raindrops are tiny prisms; white light is bent, refracted, by each tiny prism and a rainbow appears

IV. Lenses: _____________ glass

A. Concave lens – curves _______; rays spread out and away from each other; causes a virtual, or right-side up, image

IV. Lenses: transparent glass (cont.)

B. Convex lens – curves _____, but the light is manipulated inward; it brings the rays of light together. Depending on the position you are in relation to the focal point, the image formed may be virtual (right-side up) or real (upside-down) images.

V. Primary and Secondary ‘colors’ of LIGHT

RED, BLUE, GREEN are the primary colors of light. If you mix any TWO of these colors, a secondary color will be produced. For example, red and green LIGHT will produce YELLOW light. These are called secondary colors. Mixing LIGHT makes it lighter, or closer to WHITE.

Primary and Secondary Colors of PIGMENT

Paints, markers, and inks are created out of different pigmentspigments that are designed to reflectreflect certain colors of light. The primary colors of PIGMENTS are CYAN, MAGENTA, and YELLOW. When they mix, you get secondary colors that get DARKER.

Color Review

I. You see an object as the color of light it reflects. All the colors of light you don’t “see” are absorbed by the object.

II. Combining colora. White light’s primary colors are:

• Red• Green• Blue

b. Pigments are opaque substances that reflect particular colors. There are three primary pigment colors:• Cyan• Yellow• magenta

Cornea:

• Clear surface of eye

• Protects the interior eye

• curved so light bends

• Eyelids wash it clean

Iris:

• Ring of muscle

• Changes size of pupil

• Is the ‘colored’ part of the eye

Pupil:

• A hole in the iris

• Changes size when iris contracts/expands

• The wider it opens, the more light can enter the eye

Lens:

• transparent so image can pass through

• Changes shape as the ciliary muscles expand or contract to focus an image

Ciliary Muscles:

• Pull on the lens to change its shape

Retina:

• Layer of cells lining the inside of the eyeball

• Image is formed upside-down on the retina

• The cells on the retina are light-sensitive; cells generate nerve signals when hit by light

• rods: black, white, shades of gray (see in dim light, allow night vision)

• cones: detect red, green, and blue light (only function well in bright light)

Optic Nerve:

• Thick band of nerves that sends the images to the brain

• Where the optic nerve is located there are no rods or cones so light that hits on this point is not received; spot is called the blind spot

Nearsightedness (eye too long): can see nearby well; objects at a distance are

blurry because the focal point of the rays entering the eye doesn’t project on the

retina.

Farsightedness (eye too short): can see far away well; objects that are close or

near are blurry because the focal point of the rays entering the eye doesn’t land on

the retina.

Using Light

Telescopes: collect and focus light from far away objects

• Refracting: uses lens

• Reflecting: uses mirrors

Is HST a refracting or reflecting telescope?

Because HST uses a mirror, it is a reflecting

telescope.

Microscopes: collect and focus light reflecting off very small objects; uses lenses to refract the light and change the size

                                                                        

Reflection of light. Study this image carefully. Write a paragraph detailing your observations. Be sure to use the terms opaque, translucent/transparent, reflect/refract, convex/concave, plane, virtual, real, and absorb in your paragraph. Explain WHY each thing that you observe is occurring.

Follow the path of the red light. In writing, describe each change in its journey and what caused the change. Repeat for the green and then the blue light. Finally, be sure to tell what happened and the ending result at the location marked with an arrow.