Properties of Light Part 1

Properties of Light Properties of Light Light travels in straight lines: Laser

Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.

Light travels much faster than sound. For example: 1)Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.

We see things because they reflect light into our eyes: Homework

Reflection What does the term reflection mean? This occurs when a wave bounces off of a material. Light reflecting from an object is what makes it visible

Reflection When light hits a surface, some of it bounces off or is reflected. Mirrors are very shiny surfaces designed to reflect nearly all the light that hits them.

Reflection Reflection is most likely the property of light that we experience most often. Looking at yourself in a mirror, seeing the reflection of the sun in the ocean at sunset, and the sight of a mirage on the hot desert sand are all examples of reflection. In fact, everything you can see is the result of a complex pattern of light reflecting off the surface of something.

Shadows Shadows are places where light is “blocked”: Rays of light

color White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

The colors of the rainbow: Red Orange Yellow Green Blue Indigo Violet

Seeing color The color an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected

A white hat would reflect all seven colors: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue): Purple light White light

Using colored light If we look at a colored object in colored light we see something different. For example, consider a football kit: White light Shorts look blue Shirt looks red

In different colors of light this kit would look different: Red light Shirt looks red Shorts look black Blue light Shirt looks black Shorts look blue

Red Magenta White Yellow BlueGreen Cyan

How do we see color? Color originates in light. Sunlight, as we perceive it, is colorless. In reality, a rainbow is testimony to the fact that all the colors of the spectrum are present in white light. As illustrated in the diagram below, light goes from the source (the sun) to the object (the apple), and finally to the detector (the eye and brain).

Refraction What does the term refraction mean? Refraction occurs when the path of light wave changes as it moves from one material to another.

The picture of the ruler appears to be broken, even thought it is not. It appears broken because light travels through water and glass at different speeds. The light waves refract or bends as they pass from water to glass to air.

Refraction In Our World How is refraction put to good use? Devices that refract light include eyeglasses, contact lenses, cameras, microscopes, and telescopes.

Review Questions for Test 1.Define the terms reflection and refraction. 2.Briefly discuss how we see color. 3.Name a tool that is used in our world to reflect light.

Review continued 4. Name a tool in our world that refracts light? 5. In the picture of the ruler, what makes the ruler appear as if it is broken?