(2) Two edges of the paper pass through two endpoints. According to the law of reflection, when a beam of vertical parallel light hits the plane mirror M at an incident angle of 45, the reflected light will be emitted horizontally, and the intersection with the glass is the shadow of the paper; The two ends of the paper form two outermost rays. When a beam of vertical parallel light hits the plane mirror M at an incident angle of 45 degrees, reflected light is generated according to the law of reflection. After secondary reflection, the reflected light is emitted horizontally, and the intersection with the glass is the shadow of the paper. See figure (b) and figure (c).
(3) The biggest disadvantage of the camera shown in Figure (d) is that the scene seen in the viewfinder is inverted. The analysis is as follows: the lens of the camera is equivalent to a convex lens, which makes the distant object become an inverted real image on the film. After being reflected by plane mirrors M and N, the image is still inverted on the ground glass of the viewfinder, as shown in Figure (d). When we use single arrow and double arrow to represent the light beam respectively,
If n is replaced by a pentagonal prism, as shown in figure (e), this problem can be solved. As can be seen from the figure, the upper side of the incident beam passes through the M and pentagonal prism and then goes to the lower side, so the inverted image is indeed reversed.