UNIT 1: WAVES Lesson 2 Introduction: Light

Remember… Light waves do not need a medium to travel through. What are the type of waves called that do not need a medium?

Yes…They are called Electromagnetic Waves! …or EM waves.  These waves consist of changing electric and magnetic fields.  A field is a region around an object that can exert a force on another object without touching that object (like a magnet attracting a paperclip).  EM waves are transverse waves.

The Electromagnetic Spectrum What is the difference between all of these types of waves?

Behavior of Light Waves When light waves hit an object, they can be…  Reflected  Refracted  Absorbed  Scattered  Transmitted

Reflection …Reflection is when a wave bounces off of an object (this can happen with light and other types of waves, too) …Reflection is what allows you to see an object that does not emit its own light.  Does your desk produce its own light?  Than how can you see it?

The Law of Reflection …states that the angle of incidence is equal to the angle of reflection. Light Source

Refraction …Refraction is the bending of a wave as it passes from one medium to another.  This happens when light enters the water from the air. Light can travel really fast through the air, but once it hits the water, the wave slows down, causing the wave to bend.

Refraction! Refraction is why the straw looks like it is broken!

Absorption and Scattering  Absorption and Scattering is important when understanding how we see color.  If you see a green leaf, it appears green because green light is being reflected while all other light waves are being absorbed (red, blue, etc.)  The sky appears blue because the air particles scatter (move in all directions) the blue light more than any other color.

Transmission of Light  The passing of light through matter – like air or a window.

Light and the Eye 1. Light is refracted as it passes through Cornea (clear protective membrane). 2. Light passes through the pupil, the opening to the inside of the eye. 3. The iris, which is the colored part of the eye, controls how much light enters the pupil. 4. The lens focuses the light and forms an image onto the back of the eye. 5. The back of the eye, called the retina, contains the cones and rods, which receive the image. 6. The optic nerve is attached to the rods and cones and carry the information about the image to the brain. (white part)