Grade 10 Applied Science Optic (Physics)

Grade 10 Applied Science – Optic (Physics) Drawing Ray Diagrams – Basic Rules

The rules are almost the same for both curved mirrors and curved lenses.

In a curved mirror, there are five important parts. 1. The type of curved mirror a. Concave or Converging (light rays come together) b. Convex or Diverging (light rays go apart) 2. The line that meets the exact middle of the mirror. This is the PRINCIPAL AXIS 3. The point where the Principal Axis meets the mirror. This is the VERTEX 4. The middle of the curved mirror if it were a complete circle. This is the CENTRE OF CURVATURE…or the centre of the circle 5. A point on the Principal Axis midway between the Vertex and the Centre of Curvature. This is the FOCAL POINT.

To draw a ray diagram, we need to know the reflected travel of at least two of light rays…although three may be better. We will learn two rules.

These rules apply to both a concave mirror and a convex mirror. They do NOT change.  RULE #1 – A light ray that travels PARALLEL to the Principal Axis will reflect off the mirror on an angle so that the reflected light ray runs back through the Focal Point  RULE #2 – A light ray that travels through the Focal Point will reflect off the mirror at an angle so that they reflected light ray runs back parallel to the Principal Axis

Any image produced by the reflection can be described with four traits. The acronym is SALT.  S = Size (bigger, smaller, same size)  A = Attitude (Upright or Inverted)  L = Location (In front of the mirror or Behind the mirror)  T = Type (Real (i.e., actual light) or Virtual)

NOTE: The two rules for drawing hold true for lenses too.