सिल्वर दर्पण प्रतिक्रिया किस युग्म में विभेद के लिए प्रयुक्त होती है-

Explanation

In case of silvered mirrors, approximately `98%` of the light is reflected back. Thus in periscope made of a pair of silvered mirror, `4%` of the light will be damped and hence the periscope will be less efficient in case of low lights. However, when a pair of prism is used in a periscope, total internal reflection of light takes place and `100%` of the light incident on first prism is reflected on second prism. As there is no loss in light in a periscope made of prisms, it is more efficient than the silvered mirror one.