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A ray of light is incident on a concave ...

A ray of light is incident on a concave mirror . It is parallel to the principal axis and its height from principal axis is equal to the focal length of the mirror. The ratio of the distance of point B to the distance of the focus from the centre of curvature is (AB is the reflected ray)

A

`(2)/(sqrt(3))`

B

`(sqrt(3))/(2)`

C

`(2)/(3)`

D

`(1)/(2)`

Text Solution

Verified by Experts

The correct Answer is:
A

In `triangle ACD :"sin"theta= (f)/(2f) implies theta= 30^(@)`
`PB = R-(R)/(2)"sec"theta = R - (R)/(sqrt(3))`
PC = R implies CB = PC- PB = R-R + (R)/(sqrt(3))`
=`(R)/(sqrt(3)) = (2f)/(sqrt(3)) therefore (CB)/(f) = (2)/(sqrt(3))`
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Knowledge Check

  • A ray of light is incident on a concave mirror. If it is parallel to the principal axis, the reflected ray will

    A
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    B
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    centre of curvature

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    A
    pass through the pole
    B
    pass through the focus
    C
    retrace its path
    D
    be parallel to the principal axis

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