Refraction and Lenses

Refraction

1. the bending of light as it is transmitted through transparent material

2. the bending of a wave as it crosses the boundary between two media at an angle

• what happens when a light wave passes from air into water at an angle?

  • its speed decreases and causes the light ray to refract toward the normal

• what would happen to a light wave if its speed increases during refraction?

  • it would bend away from the normal

• why does refraction occur?

  • due to wave changing speed becuase light travels fastest in air, slower in liquids, and slowest in solids

• what is the index of refraction and what is it denoted by?

  • the ratio of the speed of light in a vacuum to a given material; n

• what formula represents the index of refraction?

  • n = c/v

• what is Snell’s Law?

  • a formula used to describe the relationship between the angles of incidence and refraction when refering to light or other waves passing through a boundary between two different media. it describes how light bends when traveling from one medium to the next.

• what is the formula for Snell’s Law?

  • n1sinx1 = n2sinx2

• why do objects appear at a different place from where they really are?

  • due to refraction

• what can cause a noticiable change in light speed?

  • air temperature

• what is a mirage?

  • a distorted image caused by a refraction of light in Earth’s atmosphere

• what temperature does light travel fastest in?

  • hot air

• how do you know if the light is bending towards or away from the normal?

  • if it is traveling from a lower n to a denser region with a higher n, it will bend towards the normal because it’s slowing down; vice versa for bending away

• what is an internal reflection?

  • a consequence of the refraction of light

• when does total internal reflection occur?

  • when the angle of incidence is larger than the critical angle and light is going from a slower moving medium to a faster moving medium

• what are optical fibers?

  • light pipes; transparent fibers that transport light from one place to another

• what is dispersion?

  • the separation of white light into colors arranged according to their frequency

Lens

• a piece of glass or plastic that refracts light

• forms an image by bending parallel rays of light that pass through it

• what do all lenses has to rely on?

  • on light having a slower speed in the lens, going from gas (air) to solid (lens)

• what is a converging lens?

  • aka convex lens, thicker in the middle and thinner at the edges, causing rays of light to appear to originate from a single point

• what is a diverging lens?

  • aka concave lens, thinner in the middle and thicker at the edges, causing the rays of light to appear to originate from a single point, but the refracted rays do not form a true focal point

• what kind of contact lenses do far-sighted use?

  • convex

• what kind of contact lenses do near-sighted use?

  • concave