Why is a normal eye not able to see clearly the objects placed closer than 25cm? [3 MARKS]
Why is a normal eye not able to see clearly the objects placed closer than 25cm? [3 MARKS]
Each point: 1 Mark
1. The ability of the eye lens to adjust its focal length is called accommodation.The focal length of the eye lens cannot be decreased below a certain minimum limit. When we try to read a printed page by holding it very close to our eyes it seems like the image being blurred and we feel strain in the eye.
2. To see an object comfortably and distinctly, we must hold it at about 25 cm from the eyes. The minimum distance, at which objects can be seen most distinctly without strain, is called the least distance of distinct vision. It is also called the near point of the eye.
3. For a young adult with normal vision, the near point is about 25 cm. The farthest point upto which the eye can see objects clearly is called the far point of the eye. It is infinity for a normal eye. Therefore normal eye can see objects clearly that are between 25 cm and infinity.
Each point: 1 Mark
1. The ability of the eye lens to adjust its focal length is called accommodation.The focal length of the eye lens cannot be decreased below a certain minimum limit. When we try to read a printed page by holding it very close to our eyes it seems like the image being blurred and we feel strain in the eye.
2. To see an object comfortably and distinctly, we must hold it at about 25 cm from the eyes. The minimum distance, at which objects can be seen most distinctly without strain, is called the least distance of distinct vision. It is also called the near point of the eye.
3. For a young adult with normal vision, the near point is about 25 cm. The farthest point upto which the eye can see objects clearly is called the far point of the eye. It is infinity for a normal eye. Therefore normal eye can see objects clearly that are between 25 cm and infinity.
