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A ray of light is incident along a line which meets another line 7 x - y + 1 = 0 at the point 0 , 1 . The ray is then reflected from this point along the line y + 2 x = 1 . Then the equation of the line of incidence of the ray of light is :

Options

  1. A41 x - 25 y + 25 = 0
  2. B41 x + 25 y - 25 = 0
  3. C41 x - 38 y + 38 = 0
  4. D41 x + 38 y - 38 = 0

Correct answer

C. 41 x - 38 y + 38 = 0

Step-by-step solution

Let slope of incident ray be m . ∴ angle of incidence = angle of reflection ∴ m - 7 1 + 7 m = - 2 - 7 1 - 14 = 9 13 ⇒ m - 7 1 + 7 m = 9 13     o r   m - 7 1 + 7 m = - 9 13 ⇒ 13 m - 91 = 9 + 63 m , or 13 m - 91 = - 9 - 63 m ⇒ m = -2 or m = 41 38 ⇒       y - 1 = 41 38 x - 0 ⇒ 38 y - 38 - 41 x = 0

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