Instead, most ray diagrams use at least two rays. The figure below shows two light rays that come from the object, ray a and ray b. Ray a, when reflected, enters the lower part of the lens of the eye. Ray b enters the upper part. These aren't the only light rays that enter the eye, but they do form the upper and lower boundaries of full range of light entering the eye (forming a cone in 3 dimensions). (The lens of the eye focuses these rays so that they converge to a point on the retina, allowing the eye to see the object.) b Two rays of light begin at a lightbulb and travels up and to the right, striking a vertical mirror at two points next to one another. The rays are then reflected up and to the left, ending at the top and bottom of an obsever's eye. The reflected rays are labeled a and b. The lines between the mirror and the observer's eye are extended behind the mirror as dashed lines which continues down and to the night. The dashed lines intersect at an image of a lightbulb, of the same size as the one in front of the mirror. a Ⓡ Note that both rays obey the law f reflection. Rays a and b strike the mirror at different angles, but for each ray, the incident angle is equal to its reflected angle. This makes the geometry work out such that if we trace reflected rays a and b backwards, they appear to emerge from a common point on the other side of the mirror. This image point turns out to be the same distance from the mirror surface as the object. So, for plane mirrors, the image distance (from the mirror) is equal to the object distance. Suppose you are looking at a mirror. Behind you is a painting hanging on a wall, which is a distance of 2.50 m from the mirror. You see the reflected image of the painting in the mirror. How far "behind" the mirror (in m) does the reflected painting appear to be? m Note that we've only dealt with light emitted from a single point source. But the same reasoning applies to extended objects-any point on the object can be treated the same way, and we find that for each point, the image of the point is the same distance from the mirror as the object. This implies that the size of an image in a plane mirror-it's apparent height and width-is the same as that of the object as well. So, if a person's height is 1.80 m, what is the height (in m) of her reflected image in a plane mirror? m