A ray of light is incident on the surface of a mirror with an angle of 40°. What will be the angle between the incident ray and the reflected ray?

Since the angle with the surface of the mirror is 40^o, the angle of incidence will be 50. (As normal is always perpendicular to the surface.)

According to the law of reflection of light, the angle of incidence is equal to the angle of reflection.

Therefore, the angle of reflection will also be 50^o. Therefore, the angle between the incident ray and the reflected ray will be 50^o + 50^o = 100^o.

Hence 100^o  is the correct answer.