Question

When does the focal length of the eyes increase?

Answer 1

Power of accommodation:

1. The process by which certain muscles (called ciliary muscles) function, to change the focal length of the eyes so that the image is clearly formed on the retina is called the accommodation of the eye.
2. This will vary for near and distant objects and also for objects moving away or towards the eye. By adjusting the focal length, the eye is actually changing its lens power. This is known as the power of accommodation of the eye.

Explanation:

1. Ciliary muscles are responsible for the change in the focal length of the eye lens.
2. It modifies the curvature of the eye lens to alter its focal length.
3. To form an image at the retina when the object is at a distance, the focal length has to be large.
4. Hence, the increase in focal length is caused due to the visualization of distant objects, resulting in a relaxed and thinner eye lens.