we are unable to see our image in a plane mirror from every angle but we can see a chair in a room anywhere. Why?

We see the image of an object in plane mirror when reflected ray from the object reaches our eye.

 

For example, if a chair is at the location A as shown in figure in front of mirror,

then incident ray is getting reflected and reflected ray reaches the eye of person whos is standing at B .

 

According to laws of reflection angle of incidence i equals angle of reflection r as shown in figure.

 

Person standing at the location B can not see his own image because reflected ray from mirror does not reach him.

According to law of relection, reflected ray due to the person standing at B will reach the point A .

 

hence the person standing at location B can not see his own image.

 

If the person is standing at the location C as shown in figure, incident ray from c is normal to plane mirror ,

hence reflected ray also normal, i.e., same direction of incident ray . In this case reflected ray reaches the eye of person.

Hence he can see his own image .