Question

a ray of light is incident on a plain mirror along a vector i+j+k. The normal on the incidence point is along i+j. find unit vector along reflected ray.​

Answer 1

Reflection of a ray of light is just like an elastic collision of a ball with a horizontal ground. Component of incident ray along the inside normal gets reverse while the component perpendicular to it remains unchanged. Thus the component of incident ray vector A = i + j - k parallel to normal , i.e., i + j gets reversed while perpendicular to it i.e., -k remains unchanged. Thus, the reflected ray can be written as, R = - i - j - k A unit vector along the reflected ray will be,Read more on Sarthaks.com - https://www.sarthaks.com/226270/ray-of-light-is-incident-on-plane-mirror-along-vector-the-normal-on-incidence-point-is-along.