A ray of light is incident along a line which meets another line 7 x - y + 1 = 0 at the point 0 , 1 . The…

A ray of light is incident along a line which meets another line 7x-y+1=0 at the point 0,1. The ray is then reflected from this point along the line y+2x=1. Then the equation of the line of incidence of the ray of light is :
  1. 41x-25y+25=0
  2. 41x+25y-25=0
  3. 41x-38y+38=0
  4. 41x+38y-38=0

Solution

Let slope of incident ray be m.

∴ angle of incidence = angle of reflection

∴ m-71+7m=-2-71-14=913

⇒m-71+7m=913  or m-71+7m=-913

 ⇒13m-91=9+63m, or13m-91=-9-63m

⇒ m=-2 or m=4138

⇒   y-1=4138x-0

⇒ 38y-38-41x=0

Asked in: JEE Main 2016 (10 Apr Online)

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