InterviewSolution
Saved Bookmarks
| 1. |
From the focus `(-5,0)` of the ellipse `(x^(2))/(45)+(y^(2))/(20) =1`, a ray of light is sent which makes angle `cos^(-1)((-1)/(sqrt(5)))` with the positive direction of X-axis upon reacting the ellipse the ray is reflected from it. Slope of the reflected ray isA. `-(3)/(2)`B. `-(7)/(3)`C. `-(5)/(4)`D. `-(2)/(11)` |
|
Answer» Correct Answer - D Let `theta = cos^(-1) ((-1)/(sqrt(5))) rArr cos theta = (-1)/(sqrt(5)) rArr tan theta =-2` Foci are `(+- 5,0)` Equation of line through `(-5,0)` with slope `-2` is `y =- 2(x+5)` or `y =- 2x -10` This line meets the ellipse above X-axis at `(-6,2)` Reflected ray passes through the other focus `(5,0)` `:.` Slope `= (2-0)/(-6-5) =- (2)/(11)` |
|