Electromagnetic Spectrum:Light

• Light is a form of energy

• Nothing travels faster than light (186,000 mi/sec)

• Our eyes can change visible light energy waves into something we can see

What is light?

• Visible light energy is just one form of light energy and it can be seen.

• Invisible light energy is light we cannot see:•Infrared•Ultraviolet•Radio•X-ray

• Light is a form of energy formed by a combination of electrical and magnetic rays=

ELECTROMAGNETIC WAVES

What is light?

Light EnergyLike sound:•Light travels in waves that have certain wavelengths and frequencies•Its speed is different in different materials•It can be reflected or absorbed, or it can pass through an object

Light EnergyUnlike Sound:•Light is not a vibration •Light can travel through a vacuum•Light travels more slowly through water and air•Light is a form of electromagnetic radiation

• Light travels in a straight line in all directions from its source.

• It will continue to travel in a straight line until it hits something.

• When light hit something, different things can happen. It will be either: •reflected, •refracted, or •opaque

How light behaves.

Reflection

Refraction

Light can be….

Reflection Reflection-when light hits a particular surface and bounces back.

Refraction of Light: The bending of light due to a change in its speed. The differences are caused by the changing speed of the light as it transitions to different mediums.

Example: A straw appears bent in a glass of water. A swimming pool appears shallower than it really is.

Refraction

Refraction

Light can be….

Transparent-Light and matter

• When light hits something it may be transparent.

• Transparent-allows almost all the light to pass through with very little bending or scattering of the rays. You can see through it.

• Examples: eyeglasses, empty clear glass, clear window.

The waves can pass through the object

The waves can be absorbed by the object

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Translucent- Light and Matter

Translucent- allows only some light to pass through, yet scatters and bends the rays. You can see through it, but not clearly. Examples: frosted glass, clouds, thin paper

Opaque-light can not pass through, thus creating a shadow.

Examples: cardboard, brick, solid wood, door.

Opaque

The waves can be scattered off the object.

• Light contains all the colors of the rainbow: ROYGBIV

• Color is a product of visible light energy.

• Color is created when light waves vibrate at different frequencies.

• Most colors are made from mixing together three colors: red, blue, and green

How do we see color?

Electromagnetic Spectrum

Wavelength getting smaller = waves closer togetherThese waves are always transverse waves and do not need a medium to travel.

Red, Green, and Blue are primary colors

http://www.youtube.com/watch?v=sxivAEGm4KM

Absorption and color

Why is a black car hotter than a white car in the summer?(Remember light is energy. Heat is another form of energy.)

Absorption and color

A white car reflects all wavelengths of light.A black car absorbs all wavelengths of light, absorbing the energy and turning it to heat.

Eye

• The round black parts of your eye that lets light travel through it .

• It controls the amount of light that enters the eye

• In the dark- pupils are bigger to let in more light

• In the light- pupils are smaller to let in less light.

Pupil

Cornea is the transparent outer layer of the eyeball. It covers the iris and the pupil.

Cornea

• Iris is the colored part of the eye

• It is usually blue, green, or brown

• Muscles in the iris controls the pupil

Iris

Lens are under the cornea and together they bend the light to project an upside image on the retina

Lens

• Retina is the lining at the back of the eyeball that’s sensitive to light.

• It sends messages to the optic nerve. It is a like a movie screen. The retina is the back part of the eye that contains the cells that respond to light.

• These specialized cells are called photoreceptors.

• There are 2 types of photoreceptors in the retina: rods and cones

Retina

The rods are most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. Rods are not good for color vision.

The cones are not as sensitive to light as the rods. However, cones are most sensitive to one of three different colors (green, red or blue).

Cones and Rods

Optic Nerve is a bundle of nerves that sends messages between the retina and the brain.

Optic Nerve