RRB NTPC Prelims Model Paper 5 with solutions

(3) A periscope works by using two mirrors to bounce light from one place to another. Atypical periscope uses two mirrors at 45 degree angles to the direction one desires to see. The light bounces from one to the other and then put to the persons eye. Periscopes are often used by the army to see above or around a wall or obstacle.