Ask your teacher in a choir practice room, two parallel walls are 4.00 m apart. the singers stand against the north wall. the organist faces the south wall, sitting 0.680 m away from it. to enable her to see the choir, a flat mirror 0.600 m wide is mounted on the south wall, straight in front of her. what width of the north wall can the organist see

4m

Explanation:

Since the angle of incidence of a plane mirror can be anything from 0 to 90°

Assuming that the place is a perfectly square 4×4m room

The incident ray would be 45° for the choir(object) at a 4m distance, this is still within the range of values.

We do not forget also, that the focal length of a plane mirror is infinity, the organist would in fact see farther than 4m if need be. And wider

no. dot product   =0 when vecs at right angles