Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Straight Lines and Pair of Straight Lines question

2013 · Shift 0 · Q38
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Mathematics
  4. /Straight Lines and Pair of Straight Lines
  5. /2013 · Shift 0 · Q38

Straight Lines and Pair of Straight Lines question

2013 · Shift 0 · Q38

JEE MainMathematicsStraight Lines and Pair of Straight LinesMCQ+4 / −1
A ray of light along x+3y=3x + \sqrt 3 y = \sqrt 3x+3​y=3​ gets reflected upon reaching XXX-axis, the equation of the reflected ray is :
  1. A
    y=x+3y = x + \sqrt 3y=x+3​
  2. B
    3y=x−3\sqrt 3 y = x - \sqrt 33​y=x−3​
  3. C
    y=3x−3y = \sqrt 3 x - \sqrt 3y=3​x−3​
  4. D
    3y=x−1\sqrt 3 y = x - 13​y=x−1
View written solutionFree

Correct answer: B

  1. Given line of incident ray

The ray travels along x+3 y=3.x + \sqrt{3}\,y = \sqrt{3}.x+3​y=3​.

Rewrite in slope-intercept form: 3 y=−x+3\sqrt{3}\,y = -x + \sqrt{3}3​y=−x+3​ y=−13x+1.y = -\frac{1}{\sqrt{3}}x + 1.y=−3​1​x+1.

So the slope of the incident ray is m1=−13.m_1 = -\frac{1}{\sqrt{3}}.m1​=−3​1​.

  1. Reflection from the xxx-axis

Reflection in the xxx-axis changes every point (x,y)(x,y)(x,y) to (x,−y)(x,-y)(x,−y).

For a line making angle θ\thetaθ with the positive xxx-axis, reflection in the xxx-axis changes the angle to −θ-\theta−θ, hence the slope changes from mmm to −m-m−m.

Therefore the reflected ray has slope m2=−m1=13.m_2 = -m_1 = \frac{1}{\sqrt{3}}.m2​=−m1​=3​1​.

  1. Point where the ray hits the xxx-axis

On the xxx-axis, y=0y=0y=0. Substitute into the given line: x+3(0)=3x + \sqrt{3}(0) = \sqrt{3}x+3​(0)=3​ x=3.x = \sqrt{3}.x=3​.

So the point of reflection is (3,0).(\sqrt{3},0).(3​,0).

  1. Equation of reflected ray

Using point-slope form with slope 13\frac{1}{\sqrt{3}}3​1​ through (3,0)(\sqrt{3},0)(3​,0): y−0=13(x−3).y - 0 = \frac{1}{\sqrt{3}}(x-\sqrt{3}).y−0=3​1​(x−3​).

Multiply by 3\sqrt{3}3​: 3 y=x−3.\sqrt{3}\,y = x - \sqrt{3}.3​y=x−3​.

  1. Match with options

This is exactly Option B.


Correct answer: 3 y=x−3\boxed{\sqrt{3}\,y = x - \sqrt{3}}3​y=x−3​​

PreviousNext

More from Straight Lines and Pair of Straight Lines

  • If the line 2x+y=k passes through the point which divides the line segment joining the points (1,1) and (2,4) in the ratio 3:2, then k equals :2012 · MCQ
  • The line L given by 5x​+by​=1 passes through the point (13,32). The line K is parrallel to L and has the equation cx​+3y​=1. Then the distance between L and K is :2010 · MCQ
  • The lines p(p2+1)x−y+q=0 and (p2+1)2x+(p2+1)y+2q =0 are perpendicular to a common line for :2009 · MCQ
  • The shortest distance between the line y−x=1 and the curve x=y2 is :2009 · MCQ
  • The perpendicular bisector of the line segment joining P(1, 4) and Q(k, 3) has y-intercept -4. Then a possible value of k is :2008 · MCQ
  • Let A (h,k), B (1,1) and C (2,1) be the vertices of a right angled triangle with AC as its hypotenuse. If the area of the triangle is 1 square unit, then the set of values which ′k′ can take is…2007 · MCQ
  • A straight line through the point A(3,4) is such that its intercept between the axes is bisected at A. Its equation is :2006 · MCQ
  • If (a,a2) falls inside the angle made by the lines y=2x​,x>0 and y=3x,x>0, then a belong to :2006 · MCQ