An isosceles prism has one of the refracting surfaces silvered. A ray of light is incident normally on the refracting face AB. After two reflections ray emerges from base BC normally. Then angle of prism is

72^{\circ}

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56^{\circ}

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36^{\circ}

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40^{\circ}

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Solution

The correct option is C $36^{\circ}$
From the diagram,

$2 A = θ \dots \dots \dots (1)$

$A + 2 θ = 180^{\circ} \dots \dots \dots (2)$

$\Rightarrow A + 2 \times 2 A = 180^{\circ} \Rightarrow A = \frac{180}{5} = 36^{\circ}$

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An isosceles prism has one of the refracting surfaces silvered. A ray of light is incident normally on the refracting face AB. After two reflections ray emerges from base BC normally. Then angle of prism is

The correct option is C 36∘From the diagram, 2A=θ………(1) A+2θ=180∘………(2) ⇒A+2×2A=180∘⇒A=1805=36∘

The correct option is C $36^{\circ}$
From the diagram,

$2 A = θ \dots \dots \dots (1)$

$A + 2 θ = 180^{\circ} \dots \dots \dots (2)$

$\Rightarrow A + 2 \times 2 A = 180^{\circ} \Rightarrow A = \frac{180}{5} = 36^{\circ}$