a) Why do you think our eyes fail to see object clearly at varous distances?
b) (i) Explain how image of an object is formed in the human eye
(ii) What are ciliary muscles? Explain the function of these muscles
c) Discuss the similarities and differences between the lens camera and the human eye.
a) Our eyes may fail to see objects clearly at various distances due to a condition called refractive errors. Refractive errors occur when there is a problem in the way light is focused onto the retina. This can happen because the shape of the eye is not perfectly round or the cornea (the clear front part of the eye) is not properly curved. The most common types of refractive errors are nearsightedness (myopia), farsightedness (hyperopia), and astigmatism.
To determine why our eyes fail to see objects clearly at different distances, it is recommended to visit an optometrist or ophthalmologist for an eye examination. They can perform various tests, such as an eye chart test or a refraction test, to assess the refractive errors and prescribe appropriate corrective measures like glasses or contact lenses.
b) (i) Image formation in the human eye occurs through the process of refraction and the focusing of light onto the retina. When light enters the eye through the cornea, it passes through the pupil, which adjusts its size based on the amount of light available. The iris, the colored part of the eye, controls the size of the pupil.
After passing through the pupil, the light rays go through the lens of the eye. The lens fine-tunes the focus of the light by changing shape through the action of the ciliary muscles. These muscles control the thickness of the lens, allowing it to become thicker or thinner depending on the distance of the object being viewed.
The light rays then come together and form a small, inverted, and real image on the retina. The retina contains specialized cells called photoreceptors (rods and cones) that convert the light energy into electrical signals, which are then transmitted to the brain via the optic nerve.
(ii) Ciliary muscles are muscles located within the eye. They are attached to the lens by suspensory ligaments, allowing them to control the shape of the lens. When the ciliary muscles contract, the lens thickens, increasing its refractive power for near vision. Conversely, when the ciliary muscles relax, the lens becomes thinner, decreasing its refractive power for distant vision. This process is known as accommodation.
The function of the ciliary muscles is to adjust the shape of the lens in response to objects at different distances, allowing the eye to focus properly and create clear images on the retina.
c) Similarities between a lens camera and the human eye:
1. Both have a lens that focuses light onto a receiving surface (film/sensor in a camera and retina in the eye).
2. Both utilize a diaphragm (aperture in a camera and pupil in the eye) to control the amount of light entering.
3. Both convert light energy into signals: cameras convert light into an electrical or digital signal, while the eye converts light into electrical signals that are then processed by the brain.
Differences between a lens camera and the human eye:
1. The structure of the lens in a camera is fixed, while the lens in the human eye is flexible and can change shape (accommodation) to focus on objects at different distances.
2. The camera lens has a fixed focal length, whereas the human eye has an adjustable focal length.
3. The human eye has a wider field of view and can perceive a broader range of colors and depth perception compared to a camera.
4. The camera captures a two-dimensional image, while the human eye allows for three-dimensional vision due to having two eyes that provide binocular vision.