AP EAMCET201921 Apr 2019Morning ShiftPhysicsRay OpticsActual
A girl of height 150 ~cm with her eye level at 140 ~cm stands in front of plane mirror of height 75 ~cm fixed to a wall. The lower edge of the mirror is at a height of 85 ~cm above her feet level. The height of her image the girl can see in the mirror is
Options
- A130 cm
- B140 cm
- C120 cm
- D150 cm
Correct answer
C. 120 cm
Step-by-step solution
Ray diagram of a girl standing in front of a plane mirror is given below, Applying the property of triangle and from similar triangles O P M₁ and O I₁ I₂ , = P M₁ O P = I₁ I₂ O I₁ Since, P M₁=140-85=55 ~cm Let gathered O P=a and O I₁=2 a = 55 a = x 2 a x=55 2=110 ~cm gathered So, the maximum height seen by the girl, H=110+10=120 ~cm Since, the height above her eyes, has not effected the mirror height, because it is just in front of the mirror. Hence, the correct option is (c).