Light Waves

Sec 1

Light Waves Strike objects

• Reflected• Absorbed• Transmitted

Properties of objects

• Opaque• Transparent• Translucent

Opaque

• A material that reflects or absorbs all of the light that strikes it.

Transparent

• Material transmits light

• Light passes through allowing you to see what is on the other side

Translucent

• Some light passes through

• Material scatters light as the light passes through

• You cannot see details

Reflection

• Two kinds of wave reflection

• Regular and • Diffused

Regular Reflection

• Occurs when parallel rays of light hit a smooth surface

• All the rays are reflected at the same angel

Diffuse Reflection

• When parallel rays of light hit a bumpy, or uneven surface

• The rays are reflected at different angels

Mirrors

• Sheet of glass• Smooth, silver-colored coating

• When light passes through the mirror, the back coating causes the light to reflect regularly, allowing you to see an image

Image

• Is a copy of an object formed by reflected or refracted rays of light

Plane Mirror

• Flat mirror

• Produces a image that is right-side up and

• The same size as the object being reflected

Virtual Image

• The image you see when you look in a plane mirror is a virtual image

• Right-side up or upright

Concave Mirrors

• Surface curves inward

• Can form virtual images, real images, or no image

• Depends on position of the object in relation to the focal point

Real Image

• Formed when rays actually meet at a point

• The images are upside down, or inverted

Focal Point

• The point at which the rays meet

Convex Mirrors

• A mirror with a surface that curves outward

• Images are always virtual

Refraction and Lenses

Sec 2

Index of refraction

• measure of how much a ray of light bends when it enters that material

Mirages

Is an image of a distant object caused by refraction of light

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Concave lens

• Is thinner in the center than at the edges

Convex lenses

• Is thicker in the center than at the edges

Color

Sec 3

Color

• The color of an object is the color of light it reflects

• White=reflects all colors

• Black= absorbs all colors

Primary Colors

• Three colors that can be used to make any other color

• Red, green, and blue

• Any two primary combined in equal amounts produce a secondary color

Seeing Light Waves

Sec 4

The Eye

• Organ System

• Each part plays an important part in helping you see

Cornea

• Light enter the eye through this transparent surface

• The cornea protects the eye

• It also acts as a lens bending light waves as they enter the eye

Iris

•Is a ring of muscle that contracts and expands

•This changes the amount of light that enter the eye

•Also give the eye color

Pupil

• Looks black

• As light dims, the pupil enlarges allowing in more light

• Vis versa

Lens

• Behind the pupil

• Refracts light, forming and image

• Page 257

Retina

• Layer of cells lining the inside of the eye

• Contains many of tiny, light-sensitive cells called, rods and cones

Rods

• Rods contain pigments that react to small amounts of light

• Important for seeing at night

Cones

• Respond to color

• Three types: red, blue, and green

• Function with bright

Optic Nerve

• The signals generated by the rods and cones travel to the brain along a short, thick nerve

• The brain turns the image right-side up

Correcting Vision

• Lenses in glasses are either concave or convex

• The type of lens used depends on whether the eye is too long or too short

Nearsightedness

•Person can see nearby things clearly, but objects at a distance appear blurry

•Eyeball is a little to long•Concave lens correct this

Farsightedness

• Person can see far away, but objects nearby appear blurry

• Eyeball is too short

• This is corrected with convex lenses