SU: 15
• How are power and focal length related?
a
Focal length is reciprocal of power
Focal length is reciprocal of the
square of power
C
Focal length is equal to power
d
None of the above

Focal length is reciprocal of power

Explanation:

The optical power the ability to either converge or diverge rays and it is inversely proportional to the focal length such that we express them as

where P is power and f is focal length. The unit of power is

normally called diopter D

For example, if the focal length is given as 10cm, we first convert it to meters by dividing by 100 hence f=0.1m then the power will be 1/0.1=10 D

Therefore, from the options given, Focal length is reciprocal of power or power is the reciprocal of focal length

distance = 150m

displ = root (50 ^2 + 100^2)

root(2500+10000)

root 125000