Question

# A rod of length $$10cm$$ lies along the principal axis of concave mirror of focal length $$10cm$$ in such a way that its end closer to the pole is $$20cm$$ away from the mirror. The length of the image is-

A
15cm
B
2.5cm
C
5cm
D
10cm

Solution

## The correct option is C $$5cm$$Rod $$AB$$ of length $$10 \ cm$$ lies on the axis in front of concave mirror such that end A lies at a distance of $$20 \ cm$$ from the mirror.Using mirror formula :$$\dfrac{1}{v}+\dfrac{1}{u} = \dfrac{1}{f}$$Case A :  $$u = -20 \ cm$$     $$f = -10 \ cm$$$$\therefore$$   $$\dfrac{1}{v_A}+\dfrac{1}{-20} = \dfrac{1}{-10}$$    $$\implies \ v_A = -20 \ cm$$Case B :  $$u = -30 \ cm$$     $$f = -10 \ cm$$$$\therefore$$   $$\dfrac{1}{v_B}+\dfrac{1}{-30} = \dfrac{1}{-10}$$    $$\implies \ v_B = -15 \ cm$$Thus length of image  $$L = 20 - 15 =5 \ cm$$Physics

Suggest Corrections

0

Similar questions
View More

People also searched for
View More