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Geometrical Optics question

2012 · Q86
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Geometrical Optics question

2012 · Q86

NEETPhysicsGeometrical OpticsMCQ+4 / −1
A rod of length 10 cm lies along the principal axis of a concave mirror of focal length 10 cm in such a way that its enf closer to the pole is 20 cm away from the mirror. The length of the image is
  1. A
    10 cm
  2. B
    15 cm
  3. C
    2.5 cm
  4. D
    5 cm
View written solutionFree

Correct answer: D

AIPMT 2012 Mains Physics - Geometrical Optics Question 56 English Explanation


Image position of end A

$${1 \over {{v_A}}} + {1 \over { - 20}} = {1 \over { - 10}}$$

$ \Rightarrow $ vA = - 20 cm

Image position of the end B

$${1 \over {{v_B}}} + {1 \over { - 30}} = {1 \over { - 10}}$$

$ \Rightarrow $ vB = -15 cm

Length of the image is

LA'B' = |vA| - |vB| = 20 - 15 = 5 cm
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