Light

What is light really?Electromagnetic radiation waves

• light is the range of frequencies of electromagnetic waves that stimulate the retina of the human eye

• light is a transverse wave

• Light travels in straight lines at a speed of 186,000miles per second or 3x108 m/s

• it takes 8 minutes for light to travel 93 million miles to Earth

• it would take a car traveling at 60 mph 177 years to travel that distance

• light waves have wavelengths of about 400 nm (4x10-7 m) to 700 nm (7x10-7 m)

Notice the wavelength is long (Radio waves) and gets shorter (Gamma Rays)

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.

“Just Passing Through:” What happens when light strikes

glass? Or waxed paper? Or a book?

• If light travels through an object it is =transparent

• If light is blocked by an object and a dark shadow is cast it is= opaque.

• If some light passes through but not all and a light shadow is present it is=translucent.

3 Ways to Control Light:

1.Block it-Shadows

2.Bend it-Refraction

3.Reflect it-Reflection

Blocking Lightlight travels in a straight line

shadows (the absence of light) are created when light is blocked

Bending Light

refractionchange in the direction of

waves crossing a boundary between two different media

Contact Lenses

Reflecting Light

light rays are reflected with an angle equal to the angle of incidence

Concave Mirrors

focus light to one point

Example: headlights on a car

Concave Mirrors

Convex Mirrors

reflect light outward

creates a fish eye image

Example:side view mirrorson a car