Eye

Question 1

Bright/high light intensity

Answer 1

Bright light/ high light intensity stimulates the photoreceptors in the retina and sends nerve impulse to the brain via the optic nerve to sensory neurones and carry out pupil reflex. In the iris, circular muscles contract and radial muscles relax. Pupil constricts and decreases in size. This reduces the amount of light entering the eye.

Question 2

Dim/low light intensity

Answer 2

Dim light stimulate the photoreceptors in the retina and sends information to the brain via the optic nerve and carry out pupil reflex. In the iris, circular muscles relax while the radial muscles contract. Pupil dilates and increase in size and become larger. This increases the amount of light entering the eye.

Question 3

Accommodation

Answer 3

It is the adjustment of the eye so that clear images of the objects at different distances are formed on the fovea of the retina.

Question 4

Near objects

Answer 4

Diverging light rays from near objects stimulate photoreceptors in retina and send nerve impulse to the brain via optic nerve to sensory neurones to carry out accommodation.
Ciliary muscles contract while the suspensory muscles slacken. Lens become thicker, shorter and more convex. Focal length decreases (distance between middle of lens and the point of focus on the retina). Light ray from near objects are refracted and focused on the fovea of the retina and a clear sharp image is seen.

Question 5

Distant objects

Answer 5

Parallel light rays from distant objects stimulate the photoreceptors in retina and sends information to the brain to carry out accommodation. Ciliary muscles relax while the suspensory ligament become taut. Lens become thinner, longer and less convex. Focal length increases. Light ray from the distant object are refracted and focused on the fovea of the retina and a clear sharp image is seen.