Name: Newton's Corpuscular Theory and its Limitations
Uploaded: 2019-07-19
Duration: 5 min 41 s
Description: Newton favoured the particle nature of light. Could he explain all the phenomena such as reflection, refraction, diffraction, interference, etc.? Not sure. L...

Question

What are the three rays we consider to draw ray diagrams in order to show the formation of images by spherical mirrors? How do they propagate after reflection?

Accepted Answer

Three convenient rays chosen to construct the image by a spherical mirror are:
(i) A ray parallel to the principal axis which after reflection passes or appears to pass through the focus. From the definition of principal focus, if any ray of light, travelling parallel to the principal axis, after reflection either passes through or appears to diverge from the principal focus.

(ii) A ray passing through the centre of curvature or appears to pass through the centre of curvature which retraces its path after reflection because the angle of incidence and the angle of reflection lie along the normal for a spherical mirror. In a spherical mirror, any line that joins the centre of curvature 'C' with a point on the mirror is normal to its surface at that point. Any light ray incident normally on a mirror gets reflected normally and retraces its path. As such, any light ray passing through the centre of curvature of the spherical mirror returns along the same path after reflection from the mirror.

(iii) If any ray of light initially passes through (concave mirror) or appears to pass through (convex mirror) the principal focus of the spherical mirror, after reflection, travels parallel to principal axis.

Note: In order to find the position of the image of a point source formed by a spherical mirror, we use any two of the three rays discussed above.

What are the three rays we consider to draw ray diagrams in order to show the formation of images by spherical mirrors? How do they propagate after reflection?

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