Page 404 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 31] SPHERICAL MIRRORS 389

(a) (b)
Fig. 31-4

SOLVED PROBLEM 31.2

What is the nature of the image of a real object formed by a convex mirror?
The image is virtual, erect, and smaller in size than the object, as in Fig. 31-3(b).

SOLVED PROBLEM 31.3
An object is placed at the focal point of a concave mirror. Is an image formed?
As Fig. 31-5 shows, the reflected rays are parallel to each other and so no image is formed.

Fig. 31-5

MIRROR EQUATION
When an object is distance p from a mirror of focal length f , the image is located distance q from the mirror,
where
1 1 1
+ =
p q f
1 1 1
+ =
Object distance image distance focal length
This equation holds for both concave and convex mirrors (see Fig. 31-6). The mirror equation is readily solved
for p, q,or f :

q f pf pq
p = q = f =
q − f p − f p + q

A positive value of p or q denotes a real object or image, and a negative value denotes a virtual object or
image.