PHYSICS

BEHAVIOUR OF LIGHT

ACTIVITIES

Introduction
Experiments

 

Experiments to verify the laws of reflection

Using no-parallax method
Using a ray of light
Object: The kaleidoscope
Project: Construction of a simple periscope

Using no-parallax method

Apparatus: soft board, optical pins, plane mirror, protractor and a plane sheet of paper.

Procedure:

  1. Draw a line to mark the silvered surface of the mirror on the sheet of paper.

  2. Mark a point X on the line.

  3. Draw a normal at X.

  4. Using a protractor mark off an angle of incidence, e.g. 200 and draw the incident.

  5. Stand the mirror vertically on the line representing the silvered surface.

  1. Tuck pins P1 and P2 in the incident ray.

    Note: P1 and P2 should stand vertically and far a part.

  2. Position your eye at E to view the reflections of P1 and P2.

  3. Tuck in P3 such that the images of P1, P2, and P3 appear to be in a straight line.Move your eye side ways to ensure there is no relative movement (no-parallax) between images of P1 ,P2 and P3 .

  4. Repeat procedure (ix) above with another pin P4.

  5. Join P3 and P4. It should cross the silvered line at X.

  6. Measure the angle of reflection, r.

Repeat procedures (iv) to (xii) for angles I = 300, 400, 500, 600, 700
Tabulate your results in the table below.  

i0

r0

20
30
40
50
60
70

 

What do you observe? (Generally, the angle of incidence is equal to the angle of reflection)

Teachers' guide
Scheme of work
Lesson plan

Useful web links

Making a kaleidoscope
Making a periscope