The distance of the principal focus from the pole is called the focal length (f). There is relation between object distance(u), image distance(v) and focal length(f), given by the mirror formula which is expressed as:
\(\frac{1}{v}\) + \(\frac{1}{u}\) = \(\frac{1}{f}\)
I. Magnification is given by:
a) h’/h
b) –v/u
c) Both a and b
d) None
II. The height of object is taken as positive because:
a) It is placed above the principal axis
b) It is placed below the principal axis
c) It is a real object
d) None.
III. If magnification is negative, then image is:
a) Real
b) Virtual
c) Both a and b
d) None
IV. ‘v’ is negative when image is:
a) Real
b) Virtual
c) Both a and b
d) None
V. ‘f’ is negative for
a) Convex mirror
b) Concave mirror
c) Cylindrical mirror
d) None
VI. If u = 25 cm, f = 15 cm, mirror is concave, then ν =?
a) 25 cm
b) -25 cm
c) -37.5 cm
d) None
