What is the power of normal eye lens?

**A normal eye can see objects from 25cm (near point) till infinity (far point).**

**So, we take:**

**Object distance, u = -∞ (- infinity)**

**Image distance, v = 25 cm**

**By using lens formula, we get,**

**1/v - 1/u = 1/f**

**1/25 - 1/-∞ = 1/f**

**1/f = 1/25 + 0 **** [Since, 1/-∞ = 0]**

**1/f = 1/25**

**f = 25 cm**

**For determining the power of the lens, focal length should be in metres.**

**Therefore, 25/100 = 0.25 m**

**Power, P = 1/f**

**P = 1 / 0.25**

**P = 4 D**

**Therefore, the power of a normal eye is 4 Dioptres.**

**Hope this helps u...........**

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