JEE Main 2016 · 10 Apr · Shift 1 · Mathematics Q78

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MathematicsSingle correct+4 / -1Question 78 of 90

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 :

41x − 38y + 38 = 0

41x + 25y − 25 = 0

41x + 38y − 38 = 0

41x − 25y + 25 = 0

Answer and worked solution

Official answer: A

The incident ray is the mirror image of the reflected ray in $7x-y+1=0$ . Reflecting (1, −1), a point on $y+2x=1$ , gives $\left(-\frac{38}{25},-\frac{16}{25}\right)$ . The line through it and (0, 1) has slope $\frac{41}{38}$ : $41x-38y+38=0$ .

Topics:Equations of a line

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JEE Main 2016 · 10 Apr · Shift 1, Mathematics question 78