Reflection+and+Refraction

__The Wave Nature of Light__ Light is a confusing concept to many, it is a wave, but it is a particle as well. Waves do several different things, they __reflect, refract,__ diffract, and interfere. Light can be proven to be a wave because it does those same things (though it is proven to be a particle as well).

**Refraction** Light moves at different speeds through different materials depending on the material's optical denseness. When light enters a more dense medium, it will slow down, and if it enters a less dense medium it will speed up. If the angle from the line normal to the interface (border between the two materials) is zero degrees, then the refraction that takes place is merely a change in speed. If, however, the light enters the new medium at an angle that is more than zero degrees from the normal, it will visibly "bend" towards or away from the normal line, depending on the optical density. If, in such a case, the new material is relatively more dense than the first material, the light will bend towards the normal and it will bend away from the normal line if the new material is relatively less dense. This is comparable to a cart with wheels traveling along a tile floor. The cart is cruising alone and suddenly it hits a section of carpet at a degree that is greater than zero from the normal. The wheel that hits the carpet first will slow down while the other wheels will continue going the original speed, this will cause the car to alter its course by bending down towards the normal line for the tile/carpet interface. This is refraction in an easy to understand example. Light does the same thing when it travels between media, and this is the cause of refraction.



This is a picture of the diffraction pattern through a block of glass using pins to approximate the rays of light. The light bends towards the normal when it enters the glass block that is outlined by the bold black line and the parallel pencil line. The glass block has a greater optical denseness and, therefore, a higher index of refraction; so the light slows down upon entering the glass block and will visibly appear to bend towards the normal.



This is a refraction lab in which the light rays pass into a dish of water and then into a block of glass, and then back into air. The light bends towards the normal from the water to the glass, and then away from the normal upon getting back into the air due to refraction.

**Reflection** Light as a wave can also be reflected. When light strikes upon a surface that it cannot pass through, it will reflect back the way it came at an angle of reflection that is equal to the angle of incidence. This is another picture from a lab in which we explored reflection. The light from the pin bounces off of the mirror and when it reaches your eye you get the image of the pin that appears to be behind the mirror. This experiment uses two mirrors that then reflect off themselves and create multiple images depending on the angle between the two mirrors. If you take 360 degrees and divide it by the angle between the two mirrors in degrees, you will get the number of pins you will see at that angle.

A concave mirror picture is below. The mirror reflects rays in a way that make the object look larger at this point. It's all dependent of the object's location in regards to the focal point of the mirror as well.

**We're Done** -Emily, Chloe, Kristen