Grade 12

Physical sciences

Topic: Optics(law of reflection)


Here is a quick rundown of what we will be working on:

Reflection is when light changes direction by bouncing off a surface.

When light is reflected off a mirror, it hits the mirror at the same angle (θi, the incidence angle) as it reflects off the mirror (θr, the reflection angle).

The normal is an imaginary line which lies at right angles to the mirror where the ray hits it.                                                                              .Reflection - Key Stage Wiki


Complete the following task:

  1. State the law of reflection.
  2. What happens to a ray of light when it reaches:                                                                                                                                    (a) a mirror?                                                                                                                                                                                           (b) a lens?
  3. Two flat mirrors are perpendicular to each other. An incoming beam of light makes an angle of 15° with the mirror 1, continues to mirror 2 and is reflected as shown in Figure 1. N1’N1 and N2’N2 are the normal to mirror 1 and mirror 2 respectively.


                                                           Figure. 1

  a). Calculate angles θ1 to θ3 

  b). Calculate angles θ4 to θ7

  4. Explain whether or not the path of the ray incident to mirror 1 is parallel to the path of the reflected ray from mirror 2.         


Step 1:

Learn about the Law of reflection

Step 2:

Watch this video for assistance on how to do the calculations

Step 3:

Complete the assigned task.


When doing your work make use of this mark allocation as your guide of how many marks are on each question.

Questions Marks
1 3
2(a) 2
2(b) 2
3(a) 6
3(b) 8
4 4

Total marks: [25]
The memorandum will be made available after submission.



Answer all questions                                                                                                                                                                              
Show your working (steps and reasons)                                                                                                                                                        The cover page should be typed and must be the learner’s surname and name, subject, topic and school                                                The calculations can be written by hand, scan them and combine them with the cover page and send them as a single document          Due Date: 31 May 2021 at 12H00 (Monday midday)


Teacher Page

This web quest was created to summarize the Law of reflection that is in optics on the Physical sciences subject for grade 12 learners. It is created by a final year student studying EDUCATION at CPUT. I hope it provides you with some help.