To solve this problem, we need to recall the concept of the least distance of distinct vision in human eyes.
1. Definition:
The least distance of distinct vision is the minimum distance at which the eye can see an object clearly without strain. This is also known as the near point of the eye.
2. Standard Value:
For a normal human eye, the least distance of distinct vision is taken as: 25 cm
3. Evaluating the Options:
(A) 25 m – Too large ❌
(B) 25 mm – Too small ❌
(C) 25 cm – Correct ✅
(D) 25 km – Extremely large ❌
Final Answer:
The correct option is (C) 25 cm.
A current element X is connected across an AC source of emf \(V = V_0\ sin\ 2πνt\). It is found that the voltage leads the current in phase by \(\frac{π}{ 2}\) radian. If element X was replaced by element Y, the voltage lags behind the current in phase by \(\frac{π}{ 2}\) radian.
(I) Identify elements X and Y by drawing phasor diagrams.
(II) Obtain the condition of resonance when both elements X and Y are connected in series to the source and obtain expression for resonant frequency. What is the impedance value in this case?