A submarine periscope consists of two identical rectangular plane mirrors fixed at 45∘ to the vertical, one at the top and the other at the bottom of a long tube.
(a) State the two laws of reflection of light from a plane mirror.
(b) Draw a neat, labelled ray diagram to show how a ray of light coming from an object above the water surface reaches the observer’s eye through the two mirrors.
(c) Using the diagram, explain why the final image of the object appears erect, laterally inverted, and virtual to the observer. Comment on the relative size and distance of this image compared with the object.
(d) The tube of the periscope is made longer if the submarine must stay deeper under water. Does increasing the length of the tube change (i) the path of the ray between the two mirrors, (ii) the nature or size of the image formed? Give reasons in each case.