Power of the Eye Lens at a Point Far from Infinity:

The power of the eye lens can be determined using the lens formula:

1/f = 1/v - 1/u,

where f is the focal length of the lens, v is the image distance, and u is the object distance.

Given that the point is far from infinity, we can assume that the object distance (u) is essentially equal to the distance from the retina to the eye lens, which is 2.5 cm in this case. The image distance (v) can be assumed to be the distance from the retina to the point, which is 25 cm.

Substituting the values into the lens formula:

1/f = 1/25 - 1/2.5.

Simplifying the equation:

1/f = (2.5 - 25)/62.5

1/f = -22.5/62.5

f = -62.5/22.5

f ≈ -2.78 cm.

The negative sign indicates that the lens is a diverging lens.

Hence, the power of the eye lens when forced at a point far from infinity is approximately -2.78 diopters.

Power of the Eye Lens at a Point Near:

To calculate the power of the eye lens at a point near, we can use the same lens formula as mentioned earlier.

Given that the object distance (u) is now 25 cm (the distance from the retina to the point) and the image distance (v) is now 2.5 cm (the distance from the lens to the retina), we can substitute these values into the lens formula:

1/f = 1/2.5 - 1/25.

Simplifying the equation:

1/f = (25 - 2.5)/62.5

1/f = 22.5/62.5

f = 62.5/22.5

f ≈ 2.78 cm.

The positive sign indicates that the lens is a converging lens.

Therefore, the power of the eye lens when forced at a point near is approximately +2.78 diopters.

In conclusion, the power of the eye lens varies depending on the object distance and the image distance. When the eye lens is forced at a point far from infinity, the power is approximately -2.78 diopters as the lens acts as a diverging lens. Conversely, when the eye lens is forced at a point near, the power is approximately +2.78 diopters as the lens acts as a converging lens.