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A beam of light from a source L is incident normally on a plane mirror fixed at a certain distance x from the source. The beam is reflected back as a spot on a scale placed just above the source I. When the mirror is rotated through a small angle θ, the spot of the light is found to move through a distance y on the scale. The angle θ is given by
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y x -
x 2y -
x y -
y 2x
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Correct Option: D
When mirror is rotated by angle θ reflected ray will be rotated by 2θ.
= 2θ ⇒ θ = | |||
x | 2x |