Explain the changes in pupil size and light intensity as a lamp moves away from the eye, and the physiological response of the eye, including the roles of the sympathetic nervous system and iris muscl

Here are the answers to Question 14:

14.1

• a) The lamp was furthest from the eye at Position 7.
• b) As the lamp moves further away from the eye, the intensity of light reaching the eye decreases. In response to lower light intensity, the pupil dilates (gets larger) to allow more light to enter the eye. Position 7 shows the largest pupil diameter (4.8 mm), indicating it received the least amount of light, meaning the lamp was furthest away.

14.2
When the lamp was moved from position 1 to position 2, the lamp moved further away, causing a decrease in light intensity reaching the eye. In response, the pupil diameter increased from 1.2 mm to 1.8 mm, a process known as pupillary dilation. This change is a reflex mechanism involving the muscles of the iris:

• The radial muscles of the iris contract.
• The circular muscles of the iris relax. This coordinated action pulls the pupil open, increasing its diameter to allow more light to enter the eye, thereby enhancing vision in dimmer conditions. This reflex is controlled by the sympathetic nervous system.