Question

Give MKS unit for the power of the lens.
A. meter
B. dioptre
C. weber
D. \[{\rm{mete}}{{\rm{r}}^{\rm{2}}}\]

Answer 1

Hint: The above problem can be resolved by the mathematical relation of the power of the lens. The power of the lens depends on the focal length of the lens, and it is related inversely to the focal length, as on increasing the focal length, the power of the lens increases and vice-versa.


Complete step-by-step answer
The power of the lens in its MKS unit is given by dioptre. The dioptre is that unit that is usually undertaken to measure out the refractive power of the lens. Moreover, the power of lens in its mathematical form is given by taking the reciprocal of the focal length of the lens
The relation is,
\[P = \dfrac{1}{f}\]
Here, f is the focal length in metres and P denotes the power of lens. And the reciprocal of the metre gives the fundamental unit known as Dioptre
Therefore, in MKS unit the power of the lens is denoted in terms of dioptre and option B is correct.


Note: To resolve the given problem, one must be clear about the basic units of derived and the fundamental quantities. Moreover, the correct mathematical formula for the lens's power should be known to correlate the concept and fundamentals of SI units. Besides, the significant relationship between the focal length and the lens's power is to be remembered to involve the firm solution of various related problems. Moreover, in several cases, vision defects also depend on the power of eyesight, which can be corrected by adopting the lens of desired power.