Key Concepts:•Light travels in transverse waves•Light can be reflected, absorbed,

transmitted•Parts and functions of the eye

LIGHT

Light travels in transverse waves

• Transverse means “across”. As a transverse wave moves in one direction, the particles of the medium (the material through which a wave travels) move across the direction of the wave. * This also

means light travels in a straight line

As you look into a fish tank, you are seeing the light bend as it passes through three different mediums (water, glass of the

tank, and the air). When light rays enter a new medium at an angle, the change in speed causes them

to bend or change directions. This can cause you to see

something that is not there. Other examples are mirages and

a rainbow.

Refraction of Light

When light strikes an object, it can be reflected, absorbed, or transmitted.

• Most objects reflect or absorb light. A material that reflects or absorbs all of the light that strikes it is opaque. Most objects are opaque because light cannot pass through them. Examples: wood, metal, cotton and wool fabrics.

• A transparent material transmits light. When light strikes it, it passes right through allowing you to see what is on the other side. Examples: clear glass, water, and air.

• Other materials allow some light to pass through making it translucent. Translucent materials scatter light as it passes through. You can usually tell there is something behind a translucent object, but you cannot see details clearly. Examples: frosted glass and wax paper.

• When you look at some objects, such as a shiny metal fixture or a mirror, you can see yourself but when you look at something like a book or pencil you only see the object.

• Why does that happen? You can see most objects because light reflects, or bounces off them. What you see when you look at an object depends on how its surface reflects light.

• The color of a flower depends on how it reflects light. Each flower absorbs some wavelengths of light and reflects other wavelengths. The color of an object is the color of the light it reflects.

• Objects can look a different color depending on the color of light in which they are seen.

Color

• You see objects due to series of steps that involve the structures of the eye and brain.

• Inside the retina are tiny, light-sensitive cells called rods and cones.

• Rods- contain a pigment that reacts to small amounts of light that distinguish among black, white, and shades of gray. Good during dim light and night vision.

• Cones- respond to colors. There are three types of cones that detect red light, green light, and blue light. The function only in bright light and that is why it is difficult to distinguish between colors in dim light.

Seeing Light

OPTOMETRIST-eye doctor

Correcting Vision• In some people, the eyeball is

slightly too long or too short, so the retina is slightly out of focus. Luckily, wearing glasses or contact lenses can usually correct this type of vision problem. Some lenses in eyeglasses are convex or concave depending on whether the eyeball is too long or too short.

Nearsightedness- eyeball is a little too long

• A nearsighted person can see nearby things clearly but objects at a distance become blurry. Vision seems clearer when squinting.

• Fixed with a concave lens that spread out the rays of light a little before they enter the lens of the eye.

Farsightedness- eyeball is a little too short

• A farsighted person can see distant objects clearly, but nearby objects appear blurry. Eyes also get tired when reading.

• Fixed with convex lenses that make the ray bend toward each other a little before they enter the lens of the eye.