Question 1: The human eye is a complex organ that detects light and allows us to see by converting light into electrical signals sent to the brain. Its main structures include the cornea, iris, lens, retina, and optic nerve.

Answer: The cornea, iris, lens, retina, and optic nerve are the main structures of the human eye that work together to detect light and enable vision.

Question 1: What is the primary function of the cornea in the human eye?

Answer: The cornea refracts (bends) light to help focus it onto the retina.

Question 2: Describe the role of the iris in controlling light entry into the eye.

Answer: The iris adjusts the size of the pupil to regulate the amount of light entering the eye.

Question 1: Explain the mechanism by which the iris controls the size of the pupil in bright and dim light conditions.

Answer: In bright light, the iris contracts to make the pupil smaller, reducing light entry. In dim light, the iris relaxes, causing the pupil to dilate and allow more light to enter.

Question 1: If the distance from the cornea to the retina is approximately 2.0 cm, calculate the refractive power (in dioptres) needed to focus light onto the retina. Use the formula: Refractive power (D) = 1 / focal length (m).

Answer: Refractive power = 1 / 0.02 = 50 dioptres.

Question 1: Outline the steps of a practical experiment to observe how the iris responds to bright and dim light, including safety precautions.

Answer: In a controlled environment, shine a bright light into one eye and observe the pupil constricting. Then, reduce the light intensity and observe the pupil dilating. Ensure the light source is not too intense to prevent discomfort or damage, and conduct the experiment in a darkened room for better visibility.

Question 1: A group of volunteers' pupils are measured under different light conditions. In bright light, 80% of pupils constrict to less than 3mm diameter. In dim light, 70% dilate to more than 5mm diameter. Explain what these observations indicate about the function of the iris.

Answer: These observations indicate that the iris regulates pupil size by constricting in bright light to reduce light entry and dilating in dim light to increase light entry, demonstrating its role in controlling light intake for optimal vision.

Question 1: Describe how knowledge of the eye has contributed to the development of corrective lenses and laser eye surgery.

Answer: Understanding the eye's refractive properties has enabled the creation of corrective lenses to fix vision problems like myopia and hyperopia. Laser eye surgery reshapes the cornea to correct refractive errors, improving vision without glasses or contact lenses.

Question 1: Identify and discuss one ethical issue associated with conducting experiments on the human eye or developing eye treatments.

Answer: One ethical issue is ensuring informed consent from patients before performing experimental treatments or surgeries. Researchers must also consider the risks versus benefits and avoid causing harm or discomfort, maintaining patient safety and rights as a priority.