# Optical brain

1. May 21, 2007

### Mr.IITIAN007

Rays from the sun subtend an angle theta (in radians) at the pole of a convex mirror (in radians) at the pole of a mirror of focal length f. If the diameter of the sun is D ,then diameter of the image of the sun formed by the mirror is:

(a) f theta
(b) 2 f theta
(c) 6 f theta
(d) none of these

Please tell what would be the case if the mirror is plane.

2. May 22, 2007

### mukundpa

At the pole of mirror the angle subtended by the object and image will be the same, think....

3. May 22, 2007

### Mr.IITIAN007

But , No not always . For a concave mirrror the diameter of the image becomes 2 f theta.Hey friend, perhaps this information would help-'area of the image is pie x r square and is proportional to 2f.'

Last edited: May 23, 2007