Angle between incident ray & plane mirror = 40
We know, angle b/w perpendicular & plane mirror = 90
So, angle of incidence = 90-40 = 50
According to first law of reflection,
angle of reflection = angle of incidence = 50
Total angle = Angle of reflection + angle of incidence
Total angle = 50 + 50
So,your final answer is 100 degrees
Hope this helps!
