LIGHT

Essential Questions What is visible light and how does it travel? What are reflection, refraction, and transmission? What does the visible spectrum consist of and how can we detect the components of the visible spectrum? How can we describe objects in terms of their interactions with light? What tools have been developed to take advantage of the properties of light?

Light Has Energy

There is More to Light Than What We See The colors in the rainbow make up a small portion of a huge spectrum of energy called the electromagnetic spectrum.

Visible Light is Made up of Many Colors White light is actually many colors (ROY G. BIV) –Red –Orange –Yellow –Green –Blue –Indigo –VioletWhiteLight Colors Refraction

Light Waves Different types of light have different wavelengths –Infrared (long) –Red (long) –Yellow (medium) –Violet (short) –Ultra Violet (very short) The different wavelengths are affected by objects differently Infrared Red Yellow Violet Ultra Violet 700nm 400nm

White Light White light is the visible spectrum of different wavelengths of light traveling together. Different colors of light travel at different speeds through different things like air, water, and glass. When white light moves from air to water or air to glass, the different colors of light bend at different angles. They separate into individual colors.

Refraction As light waves pass through an object its path can change. This bending is called refraction.

Reflection The bouncing of light off an object is called reflection. You see objects because the light is reflected straight back at you. Light bounces off an object like a ball bounces off of a wall. If you roll the ball straight at the wall it will bounce back straight. If you roll a ball toward a wall at an angle, it bounces away from the wall at an angle.

Different Kinds of Matter Allow Different Amounts of Light to Pass Through Transparent Translucent Opaque Transparent Translucent

Transparent Transparent objects appear clear because they transmit light energy and don’t absorb it. Light goes right through transparent matter. Example: Clear glass

Translucent Translucent matter allows a limited amount of light through. Example: wax paper

Opaque Opaque matter does not allow light to pass through. This type of matter reflects or absorbs light energy. Examples: Metal, wood, your body.

Opaque Objects also Reflect When we see an object that does not produce light it is reflecting light. A mirror reflects everything. Colored objects produce a limited reflection –They reflect some colors of light –They absorb other colors of light red Reflects red and absorbs all other colors green Reflects green and absorbs all other colors

Making a Rainbow Atmosphere and crystals separate out the light in to all the colors like a Rainbow Separating out of the light into all the colors is called refraction

Light Through the Atmosphere During daylight, the sun’s rays are diffracted by molecules in the atmosphere. The shorter wavelengths (blue, violet and purple) reflect from the atmosphere and the sky appears light blue. At sunset, when rays of the sun’s light travel much farther through the atmosphere, green and yellow light is diffracted. The sky reflects orange. Morning Evening

Lenses Lenses are the basic component of most optical tools –Eyeglasses –Magnifying glass –Telescopes –Microscopes –Camera –Etc. Lenses are used for form images Lens

Eyeglasses One of the oldest technologies to use light to benefit man are eyeglasses –Ground disks of glass –Bend light to assist sight In 1268 the scientist and scholar Roger Bacon mentioned the use of lenses to aid eyesight

Other Optical Tools Use Lenses Telescopes Microscopes Binoculars Cameras Even toys such as a kaleidoscope use lenses

Telescope Telescopes are designed to magnify very distant objects They concentrate light into your eye They make distant objects visible Mars

Binoculars Binoculars are double telescopes –Small enough to be held in the hand –They magnify distant objects so that they can be seen more clearly Unlike the telescope, they also allow the user to see depth or perspective –Stereoscopic effect –made by your two eyes seeing an image from slightly different angles Focus Knob Eye cup Eyepiece Adjustment Objective Lens

Microscope Magnify small objects Many objects too small to be seen with the unaided eye can be viewed through a microscope The development of the microscope greatly affected human life. Before the microscope was invented, little was known about tiny creatures, bacteria, and viruses

Light Scientists Anton von Leeuwenhoek Isaac Newton Galileo Galilei Robert Hook

Magic School Bus The Magic School Bus Gets a Bright IdeaThe Magic School Bus Gets a Bright Idea The Magic School Bus Makes a RainbowThe Magic School Bus Makes a Rainbow

PLAY A GAME Light Jeopardy Light Millionaire Computer Game: es/alienattack/alienattacklink.htm