# A mirror and a source of light are situated at the origin  and at a point on  respectively. A ray of light from the source strikes the mirror and is reflected. If the direction ratios of the normal to the plane are proportional to , then direction cosines of the reflected ray are a) b) c) d)

## Question ID - 56101 | SaraNextGen Top Answer A mirror and a source of light are situated at the origin  and at a point on  respectively. A ray of light from the source strikes the mirror and is reflected. If the direction ratios of the normal to the plane are proportional to , then direction cosines of the reflected ray are a) b) c) d)

Answer Key / Explanation : (d) -

(d)

Let the source of light be situated at , where,

Let  be the incident ray,  be the reflected ray and  be the normal to the mirror at

Direction ratios of  are proportional to  and so its direction cosines are 1, 0, 0

Direction cosines of  are

Let  be the direction cosines of the reflected ray . Then,

Hence, direction cosines of the reflected ray are