Two plane mirrors at an angle such that a ray incident on a mirror undergoes a total deviation of 240° after two reflections.

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the angle between the mirror is 60°

the number of images formed by this system will be 5, if an object is placed symmetrically between the mirrors

the no. of images will be 6 if an object is kept unsymmetrically between the mirrors

a ray will retrace its path after 2 successive reflections, if the angle of incidence on one mirror is 60°

answer is A.

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Detailed Solution

Total deviation due to two reflection

$d = 360 - 2 θ \Rightarrow 240 = 360 - 2 θ \Rightarrow θ = 60^{\circ}$

$\frac{360}{θ} = 6 . This is even. As the object is$

placed symmetrically between the mirrors
$N = \frac{360}{θ} - 1 = 5$

If the object is placed un symmetrically
$N = \frac{360}{θ} = \frac{360}{60} = 6$

When a ray incidents on M1 at 60°, it falls on M₂ normally as shown in figure

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