# Light always travels in straight lines. It will NEVER curve.

## Presentation on theme: "Light always travels in straight lines. It will NEVER curve."— Presentation transcript:

Light always travels in straight lines. It will NEVER curve.
Light sources How light travels Light travels in straight lines. If you want to prove this, look at a beam of light coming from a small torch, or find a tube or hose. You can see through the tube when it's straight, but if it's bent, you can't see anything.

Light moves very, very quickly—at 186,282 miles per second, or 299,792,458 meters per second. Light rays travel in one direction until they hit an object. Light reflects, or bounces off the object and into our eyes so we can see it. The object also absorbs, or takes in, some light. Objects that are shiny, such as metal pots and mirrors, reflect light better than dull objects such as dark sweaters or fuzzy toys, which absorb more light. Smooth, flat mirrors reflect light in roughly the same angle the light hits them so we can see reflections. When light hits curvy mirrors, it bounces off in many different directions and back to our eye. We see our reflections, but they are distorted.

Reflected light For us to see things, light has to travel from its light source to the object and then bounce off it into our eyes. We can't see behind us because the light that reflects off the things behind us doesn't make it into our eyes. Shiny smooth surfaces reflect light well. (Examples: TV, mirrors, CDs, spoons, etc.)

When you think of reflection, think of BOUNCE
When you think of reflection, think of BOUNCE. Light bounces off a shiny surface at the same angle it hits the shiny surface. Mirror

REFRACTION: Light rays usually travel in straight lines, but when they pass from one material to another they can be forced to bend (change direction and continue on a new straight path). The bending is called refraction. It happens because light travels at different speeds in different materials. If light rays travel through air and enter a more dense material, such as water, they slow down and bend into the more dense material. Light rays moving into a less dense material, such as from water to air, speed up and bend outwards. Light Notice the light coming from the air into the water gets bent as it enters the water. It bends again as it exits the water.

Refraction (Think BEND)

Refracting white light with a prism
When you think of refraction, think of BEND. During refraction, light bends as it enters and exits a medium.

Refraction example Straw in a beaker of water. The straight straw appears to be bent or broken as the light rays are refracted (bent) at the boundary between the air and the water.

SOME Common objects that refract light
Eyeglass lenses Microscopes (because of lenses) Telescope (because of lenses) Hand lens (magnifying glass) Prism Water drops when they form a rainbow

Opaque, Translucent, and Transparent
Light can easily pass through some objects, such as clear plastic or glass. These objects are transparent and we can see through them. Light cannot pass through opaque objects, such as wood blocks. Objects that block light can cast shadows. Show children that when an object blocks light, light cannot pass through to the other side. You see a dark spot that’s shaped like the object—a shadow. This is how we know that light travels in straight lines; if it curved, it would bend around opaque objects and shadows would not be made. Some objects block some light but also allow some light to pass through. Sunglasses and stained glass block some light. Translucent objects diffuse light in many different directions. It is difficult to see through translucent objects (only allow a little bit or light to pass through) such as sheer fabric, wax paper, frosted glass, or tissue paper.

Light Family Activities – Feel Free To Try