'Optics' is a section of physics that requires you to construct optical ray diagrams.
These have to be drawn very precisely. See this page for details on the symbols used.
A reflected ray is the ray that 'bounces off' the boundary between two optical media (but never use that term in an exam - always say 'reflects').
It is formed according to the Law of Reflection... see the diagram below...
There are two types of reflection you should know about.
The formation of an image in a plane mirror
The vidclip below will lead you through how to draw a ray diagram of the reflection of a point object in a plane mirror - a frequent subject set in GCSE examination questions....
This vidclip takes you through how to construct a ray diagram to illustrate the nature the image in a plane mirror - that it is virtual, ertect, laterally inverted and that each image point is formed as far behind the mirror as the corresponding object point is in front.
Now revise the topic from flash cards I have written for: