Question

a man raises his left hand infront of a plane mirror but the image facing him is raising its right hand WHY​

Answer 1

because plain mirror always  forms  laterally inverted image ...

hope it will help u ..

Answer 2

Answer:

Laterally inverted image is formed in case of a plane mirror. So if the object (person) raises his left hand then its image will raise his right hand and vice versa.

Explanation:

 If a person looks into a mirror and raises his right hand, the image in the mirror makes it look like the person raised his left hand due to lateral inversion. Although it appears that mirrors reverse images, they actually switch them from back to front in the same way that a printing press does.