Refraction Notes

The index of refraction (n) varies with wavelength of light.
- Different colors (e.g., green, purple, red) have different indices of refraction.
A common demonstration involves a prism that separates light at angles based on its color due to varying refractive indices.
- Light bends when entering and exiting the prism, producing a spectrum.

Total internal reflection occurs when light hits a boundary at an angle greater than the critical angle and does not pass into the second medium, but reflects entirely back into the first medium.
This phenomenon contributes to the visual sparkle of diamonds, which reflects internal light multiple times, creating a rainbow effect.
Example of total internal reflection:
- A light ray passing from a denser medium to a less dense medium at an angle greater than the critical angle.
- For a poorly cut denture, the angle at which light enters may not exceed the critical angle, failing to produce total internal reflection.

Refraction influences how we perceive objects submerged in water:
- Example: A straw in a glass of water or a pencil in water appears bent.
- Attention to how light rays travel to our eyes, bending at the medium interface, leads to depth perception errors.
Ray tracing illustrates how observers perceive objects due to refraction:
- Actual position vs perceived position of an object differs due to bending rays of light.
Important definitions:
- Real Image: Created when light rays converge at a point and can be projected on a surface.
- Virtual Image: Formed when light rays diverge, causing the image to appear at a location where light does not actually reach.

Ray tracing applies similarly to flat mirrors as to refraction.
Properties of flat mirrors:
- Image size is equal to object size (e.g., you are as tall as your reflection).
- Light rays do not actually go where the virtual image appears to be.
Example with Mike:
- If Mike is 20 cm from the mirror and L is 5 cm from the mirror, the image distance can also be calculated in relation to the object distance.

Spherical mirrors are created by cutting a section of a sphere:
- Focal length (f): $f = \frac{R}{2}$ , where R is the radius of curvature.
Characteristics discussed:
- Concave Mirrors: Converging mirrors where light rays focus to a point, creating real images that can be projected.
- Convex Mirrors: Diverging mirrors that produce virtual images that are upright but smaller than the object.

Key techniques for analyzing mirrors include using specific rays:
  - 1st Ray: Light ray passing through the center of curvature.
  - 2nd Ray: Light ray parallel to the principal axis reflects through the focal point.
  - 3rd Ray: Light ray directed towards the focus reflects parallel.
These rays help to determine the properties of the image produced by the mirror.

Examples of where the principles of mirrors are utilized:
- Convex Mirrors: Used in car side mirrors to provide a wider field of view.
- Shopping Department Stores: Convex mirrors are often placed in corners to enhance visibility and safety.

Encourage exploration and practical understanding:
- Experiment with different mirrors and observe how your reflection changes in size and orientation.
- Discuss image formation through ray tracing on actual mirrors or lab equipment in future classes.