Vector 3DEasy
Question
A mirror and a source of light are situated at the origin O and at a point on OX respectively. A ray of light from the source along the x-axis strikes the mirror and is reflected. If the direction ratios of the normal to the plane of mirror are 1, -1, 1, the direction cosines of the reflected ray are
Options
A.
B.
C.
D.None
Solution
The Dr′s of incident ray are (-1, 0, 0). Let the Dr′s of reflected ray be (l, m, n). Then the Dr′s of the normal to the plane of mirror will be (l-1, m, n)
So
= K(say)
l = K + 1, m = - K, n = K
l2 + m2 + n2 = 1 ⇒ K = -
So, (l, m, n) ≡
So
= K(say)l = K + 1, m = - K, n = K
l2 + m2 + n2 = 1 ⇒ K = -
So, (l, m, n) ≡
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