To calculate the strength of the eye lens, we use the formula
[tex]\frac{P}{100} = \frac{1}{f} =\frac{1}{u} +\frac{1}{v}[/tex] ( thin lens formula)
Here, u is the object distance and v is image distance.
Given, [tex]u =1 m=100cm[/tex] and [tex]v = 2 cm[/tex]
Therefore,
[tex]\frac{1}{f} =\frac{1}{100} + \frac{1}{2}[/tex]
[tex]\frac{1}{f} = 0.01 + 0.5[/tex][tex]= 0.51 cm[/tex]
Thus, strength of the eye lens is
[tex]P= \frac{100}{f} =\frac{100}{\frac{1}{0.51} } = 51 D[/tex]
