Light . What is light?. Energy You Can See. Light is a kind of energy that moves in waves away from their source. We can see objects because light reflects off them back to our eyes. Energy You Can See. Light and Matter. Light reacts to different types of matter.
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Light What is light?
Energy You Can See • Light is a kind of energy that moves in waves away from their source. • We can see objects because light reflects off them back to our eyes.
Light and Matter • Light reacts to different types of matter. • Transparent matter allows light to pass through it. • Clear window. • Translucent matter allows some light to pass through, but refracts or bends light in many directions causing the image on the other side to be blurry. • Frosted glass, wax paper. • Opaque matter does not let light pass through it at all • Wooden door, wall, person
Light and Matter Transparent opaque Translucent
Shadows • When light waves strike an opaque object some of the light hits the object blocking some of the light. • Some of the light goes around the object and hits the ground causing a shadow to form. • A shadow is a place where light does not strike.
Sharp Shadows • An object that is close to its shadow makes a small, sharp shadow. • An object that is far from its shadow makes a large, blurry shadow.
Summarize You see an object when light is reflected off of it Opaque objects block light. What is light? Transparent objects transmit light. A shadow is an area where light does not strike. Translucent objects refract light.
Light How is Light Reflected?
Reflection • Light waves move in straight lines, but change directions when it hits something. • The directions changes depending on what the light waves hit. • Light waves reflect or bounce off most objects. • When light waves hit a mirror they reflect back to your eyes and you see your image. • When light waves hit things that are not smooth the reflect back in many different directions.
Refraction • The path of light waves change when it hits some things, such as air or water. • Light waves refract or bend when they move from air to water.
Refraction • Lenses are glass objects that are curved to refract light. • There are two types of lenses. • Concave • Convex
Refraction Convex Concave
The Human Eye • Each of your eyes has a lens near the front of your eye. • When you see an object reflected light enters the lenses of your eyes and bends the light to make an image. • The image is upside down so the brain flips the image right side up.
Summarize Mirrors and other smooth surfaces reflect all the light that strikes them. Light can refract or bend, when it passes through air, water, and glass. How is light reflected? The lenses in your eyes refract that light to form an image on your retina. Your brain interprets that image.
Light What is color?
The Colors of Sunlight • White light is made up of many colors. • When white light shines through a prism the light is bent breaking the white light into many colors. • A prism is a triangular piece of glass or other transparent object that breaks white light into many colors. • Rain drops can act as tiny prisms causing the appearance of a rainbow.
Seeing Colors • When light shines on an object some of the light is absorbed or taken in and some of it is reflected. • The objects absorbs some colors and reflects other colors. • The reflected colors are the colors we see. • Bananas look yellow because they reflect yellow light and absorb the other colors.
Seeing Colors Yellow light is reflected All other colors are absorbed
Colored Light • The color of an object is based on the light it reflects and the color of light shining on it. • White light is made up of all the colors of the rainbow. • Shine a white light on a white shoe an the shoe looks white. • Shine a red light on a white shoe an it will look red.
Summarize A rainbow forms when sunlight separates into colors as it passes through raindrops. When white light strikes an object, you see only the reflected colors. The other colors are absorbed. What is color? Light affects how an object looks. White objects appear to change color under colored light.
Review • What types of surfaces reflect light MOST clearly? • Smooth and shiny • A shirt reflects blue light. It absorbs all the other light. What color is the shirt? • Blue • How can you make a sharp shadow blurry? • By increasing the distance from the object from its shadow. • What is a transparent object that can separate white light into many colors? • prism
Review • What type of object does not transmit light? • Opaque • What causes shadows? • An object blocks some of the light. • How does light reflect? • It bounces off a surface. • What type of objects cause shadows when light strikes them? • Opaque
Review • What will happen to light waves that strike the surface of a window? • They will pass through the window. • Why does a white object appear to be white? • It reflects all colors. • What objects have lenses? • Eyeglasses • Human eye • Magnifying glass • Telescope • microscope
Review • A quarts rock is what type of object? • Translucent • How do eyeglasses help correct a person’s vision? • They bend light • Explain why a strawberry is red. • It reflects red light and absorbs all other colors.
Review • Why does a person cast a shadow but a glass does not? • Only the person blocks light waves. • Sometimes you can see a rainbow when you look at a lawn sprinkler on a sunny day. Why is this so? • The water droplets separate light like a prism.