Question

In periscopes, the parallel rays entering the cylindrical tube from the upper end from an object, strike the plane mirror at an angle of _____ and hence are reflected through an angle of ________.

• A. ${30}^0,{30}^0$
• B. ${45}^0,{45}^0$
• C. ${45}^0,{30}^0$
• D. ${90}^0,{90}^0$

Answer 1

Answer: (B)

${45}^0,{45}^0$

As seen in diagram.

In periscopes, the parallel rays which enter the cylindrical tube from the upper end from an object, strike the plane mirror at an angle of ${45}^0$ and hence are reflected through an angle of ${45}^0$. These reflected rays strike the second mirror at an angle of ${45}^0$ and are further reflected through an angle of ${45}^0$.