# Electromagnetic Spectrum: Light

## Presentation on theme: "Electromagnetic Spectrum: Light"— Presentation transcript:

Electromagnetic Spectrum: Light

What is 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

ELECTROMAGNETIC WAVES
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

Light Energy Like 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 Energy Unlike 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

How light behaves. 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

Light can be…. Refraction Reflection

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

Refraction 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

Light can be….

Transparent-Light and matter
The waves can pass through the object 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 be absorbed by the object
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 . The waves can be absorbed by the object

Opaque The waves can be scattered off the object.
Opaque-light can not pass through, thus creating a shadow. Examples: cardboard, brick, solid wood, door. The waves can be scattered off the object.

How do we see color? 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

Electromagnetic Spectrum
Wavelength getting smaller = waves closer together These waves are always transverse waves and do not need a medium to travel.

Red, Green, and Blue are primary colors

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

Pupil 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.

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

Iris Iris is the colored part of the eye
It is usually blue, green, or brown Muscles in the iris controls the pupil

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

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

Cones and Rods 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).

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