Reflection in curved mirrors

Duration: 90 minutes

Grade: IX

1. Objective

To guide students to do the following:

1. Observe how the direction of the incident ray (going through the focus, running parallel to the principal axis, and going through centre of curvature) affects the direction of the reflected ray.
2. Apply the laws of reflection to verify the above findings.

2. Learning Outcomes

Apply laws of reflection to curved mirrors.

Draw ray diagrams for different orientations of incident rays.

3. Summary of Module

The module has been structured around the approach of “I Do, We Do, You Do”, which provides ample opportunities to the students for observing and understanding the concepts. The teacher should introduce the students to curved mirror and make them familiar with the associated terminologies. The teacher can demonstrate the concepts relating to how light is reflected for different orientation of incident rays—incident ray running parallel to the principal axis and other such orientations—using a cylindrical concave mirror. The students should be divided into groups and visually observe how light is reflected by a concave surface and experimentally find out the reflected rays for the given incident rays. They are expected to draw them on their worksheets.

The teacher should also explain how a normal is to be drawn and experimentally verify the laws of reflection pertaining to curved mirrors for different incident rays. Following this, the students along with the teacher should verify the laws of reflection simultaneously for another incident ray. Finally, the students should verify the laws of reflection for yet another incident ray on their own.

The procedure for making a cylindrical concave mirror using easily available materials has also been provided in this module.