Answer
a. Concave
b. Upright, virtual, magnified
c. 1.40 m
Work Step by Step
The object distance is 20.0 cm. The magnification is +1.4. Find the image distance, then the focal length.
$$m=-\frac{d_i}{d_o}$$
$$d_i=-md_o$$
Use the mirror equation, 23–2.
$$\frac{1}{d_o}+\frac{1}{d_i}=\frac{1}{f}$$
Solve for the focal length.
$$f=\frac{d_od_i}{d_o+d_i}=\frac{d_o(-md_o)}{d_o-md_o}$$
$$=\frac{(20.0cm)(-(1.4)20.0cm)}{20.0cm-1.4(20.0cm)}=70cm$$
The focal length is positive, so the mirror is concave, aka a converging mirror.
b. Find the image distance.
$$d_i=-md_o=-1.4(20.0cm)=-28.0cm$$
The image will be upright (because m is positive), virtual (because the image distance is negative), and magnified (because the magnitude of m is greater than 1).
c. The radius is twice the focal length, or r = 1.40m.