Question

The minimum length of a plane mirror required to view the full the image of 6 feet tall person is:
(A) 3 feet
(B) 6 feet
(C) 4 feet
(D) 5 feet

Answer 1

Hint: A plane mirror makes an image of objects in front of the mirror; these images appear to be behind the plane in which the mirror lies.

Formula used:
Law of reflection states that angle of incidence is equal to angle of reflection.
\[\angle i = \angle r\]
Where i is the angle of incidence and r is the angle of reflection.

Complete answer:.
We know that the image of an object is formed when rays coming from the object get reflected by the mirror and these reflected rays intersect each other.
Let us make use of the law of reflection which says angle of incidence is equal to the angle of reflection.
\[\angle i = \angle r\] (1)
Therefore, using equation (1) we can say that the minimum length of the mirror to view that full image of an object should represent the height of the object.

So, we can say that for a 6 feet tall person the minimum length of the mirror to view his full image should be 3 feet.

Hence, option (A) is the correct option.

Note:
> The top edge of the mirror should be placed exactly perpendicular to the eyes.
> Plane mirrors are the only mirror for which a real object always produces an image that is virtual, erect, and of the same size as the object. Virtual objects produce real image;
> One of the important characteristics of the image that is formed by the plane mirrors is the image is laterally inverted.
> However, the focal length of a plane mirror is infinite and its optical power is zero.