Question 1: The human eye consists of several key structures including the cornea, iris, lens, retina, and optic nerve. Each part plays a vital role in capturing and processing light to produce visual images. Understanding these structures helps explain how the eye responds to different light conditions.

Answer: The cornea, iris, lens, retina, and optic nerve are key structures of the human eye that work together to capture and process light for vision.

Question 1: Define the term 'pupil' and explain its function in the eye.

Answer: The pupil is the opening in the iris that regulates the amount of light entering the eye; it widens in low light and contracts in bright light.

Question 2: Describe how the iris adjusts in response to varying light intensities.

Answer: The iris adjusts by contracting in bright light to reduce light entry and dilating in dim light to allow more light in.

Question 3: Explain the role of the lens in focusing light onto the retina.

Answer: The lens changes shape to focus light precisely onto the retina, allowing clear images at different distances.

Question 1: Calculate the power (in dioptres) of a lens with a focal length of 0.25 meters. Use the formula: Power (D) = 1 / focal length (m).

Answer: Power = 4 dioptres

Question 2: A person’s eye can focus on objects between 25 cm and infinity. What is the range of the eye’s focusing power in dioptres?

Answer: Range: 4 dioptres to 0 dioptres (focal length from 0.25 m to infinity)

Question 1: Describe a simple experiment to test how the pupil diameter varies with different light intensities. Include the variables and safety precautions.

Answer: An experiment can be set up where a participant’s eye is exposed to varying light levels using a controlled light source. The independent variable is light intensity, the dependent variable is pupil diameter, and the control variables include distance and ambient conditions. Safety precautions include avoiding direct exposure to very bright lights to prevent eye damage.

Question 1: In a study, pupils dilated to 7 mm in dim light and constricted to 2 mm in bright light. Explain what these measurements indicate about the eye’s response mechanism.

Answer: The measurements show that the pupil dilates in low light to allow more light in and constricts in bright light to reduce light entry, demonstrating the eye’s adaptive response.

Question 1: Explain how the structure of the human eye allows it to focus on objects at different distances. Include the role of the lens and ciliary muscles in your answer. (6 marks)

Answer: The eye focuses on objects at different distances through the process of accommodation. When viewing near objects, the ciliary muscles contract, causing the lens to become thicker and more rounded, increasing its refractive power. For distant objects, the ciliary muscles relax, making the lens thinner and flatter, decreasing its refractive power. This adjustment of the lens shape ensures light rays are focused precisely onto the retina for clear vision at various distances.

Question 1: Describe how modern contact lenses and intraocular lenses (IOLs) are designed based on an understanding of eye anatomy and focusing mechanisms.

Answer: Contact lenses and IOLs are designed to correct focus by mimicking the eye’s natural refractive properties. They are shaped to adjust the eye’s focal length, helping individuals with refractive errors like myopia or hypermetropia to see clearly. Their design considers the curvature of the cornea and lens to restore proper focusing.