Q.

A light ray emits from the origin making an angle 30° with the positive x-axis. After getting reflected by the line x+y=1, if this ray intersects the x-axis at Q, then the abscissa of Q is             [2023]

1 2(3-1)  
2 32(3+1)  
3 23+3  
4 23-3  

Ans.

(3)

Given Slope of incident ray =tan30°=13

So, slope of incident ray = slope of reflected ray =13

Now, Equation of line making an angle 30° with positive x-axis and passing through origin is, y=x3

So, line y=x3 and x+y=1 intersect at (33+1,13+1)

So, equation of reflected ray is

y-13+1=3(x-33+1)

Put y=0 x=23+3