Subjects
Grades
Method for Finding the Centre of Curvature
Concept sheet | Physics
Secondary
5
Table of contents
This concept sheet explains the steps to follow to find the centre of curvature in a cylindrical mirror.
The centre of curvature is the distance between the vertex and the centre of the circle from which the cylindrical mirror was shaped. In a cylindrical mirror, the centre of curvature is located at a distance that is twice the focal length of the mirror.
Equipment
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Ray box
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Cylindrical mirror
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Sheet of paper
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Ruler
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Pencil
Procedure
The technique described below can be used with concave mirrors or convex mirrors.
1. Place the mirror in front of the ray box onto the sheet of paper.
If the procedure is carried out with the convex mirror, it is better to place the mirror in the centre of the sheet of paper in order to more easily trace the extensions of the light rays.
2. Using a pencil, draw a line along the cylindrical mirror in order to trace its reflecting surface onto the paper.
3. Turn on the ray box and send a ray of light towards the mirror so that the reflected ray and the incident ray overlap.
4. Draw a dotted line showing the position of the light ray on the paper.
5. Move the ray box and send a ray of light to the mirror again (at a location different from that of the first ray) so that the incident and reflected rays are still overlapping.
6. Draw the position of the light ray on the sheet of paper with a dotted line.
7. Remove the mirror and ray box from the sheet of paper.
8. Connect the dots to form a solid line drawn on the sheet of paper. The intersection of the two rays corresponds to the centre of curvature of this mirror.
For the concave mirror
For the convex mirror
9. Put away the equipment.