Question

A small object is placed 10 cm infront of a plane mirror. If you stand behind the object 30 cm from the mirror and look at its image, the distance focused for your eye will be(a) 60 cm(b) 20 cm(c) 40 cm
(d) 80 cm

Answer 1

I'm going to assume that since you haven't given any more information, the object is 10 cm in front of the reflective surface. In this case, you stand 30 cm, so there's 30 cm to the reflective surface + 10 cm back to the object, so this would be 40 cm.

If, however, the mirror has a glass surface, and you are measuring from the surface of the mirror, instead of the actual reflective surface, the result is slightly different. The distance is always to the reflective surface, so if the glass is 1/2 cm thick, that would put the object 10.5 cm from the reflective surface, and you would be 30.5 cm from the reflective surface. In this case, the distance would be 41 cm.

I assume you mean the first scenario though.

Answer 2

The answer is option is c) 40 m because image is at equal distance from the object.

So. 10+30
=40 m