A person can see clearly objects only when they lie between \(50~\text{cm}\) and \(400~\text{cm}\) from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use will be:

A man with hypermetropia cannot see objects closer than a distance of \(40~\text{cm}\) from the eye. The power of the lens required so that he can see objects at \(25~\text{cm}\) from the eye is:
1. \(+4.5~\text{D}\)
2. \(+4.0~\text{D}\)
3. \(+1.5~\text{D}\)
4. \(+3.0~\text{D}\)

The near point of a person is \(50~\text{cm}\) and the far point is \(1.5~\text{m}.\) The spectacles required for reading purposes and for seeing distant objects are respectively:

A boy with defective eye-sight cannot see things beyond 50 cm. The corrective lens required has the power:

1. +1 D

2. +2 D

3. -1 D

4. -2 D

A person can see objects clearly between \(1~\text{m} \)and \(3~\text{m}. \). The power of the lens required to correct near point will be:
1. \(-2.5~\text{D}\)
2. \(3~\text{D}\)
3. \(+ 1.5~\text{D}\)
4. \(- 1.75~\text{D}\)

If there had been one eye of a man, then:

The diameter of the eye-ball of a normal eye is about 2.5 cm. The power of the eye lens varies from:

1. 2 D to 10 D

2. 40 D to 32 D

3. 9 D to 8 D 

4. 44 D to 40 D