pupil
Definition
The pupil is the opening in the centre of the iris, the coloured part of the eye. The pupil allows light to enter the eye and is controlled by the iris muscles.
The size of the pupil changes in response to the amount of light available. In bright light, the pupil constricts (gets smaller) to reduce the amount of light entering the eye. In the dim light, the pupil dilates (gets bigger) to allow more light to enter the eye.
The pupil is also affected by age, medications, and medical conditions. For example, the pupil gets smaller as we age. Some medications, such as those used to treat glaucoma, can also affect the size of the pupil. And some medical conditions, such as diabetes, can also cause changes in the size of the pupil.
The pupil is an important part of the eye's ability to see. By changing size, the pupil allows the eye to adapt to different light conditions and see clearly in both bright and dim light.
How can the word be used?
The pupil of the eye is the opening in the centre of the iris.
Different forms of the word
Noun: the dark opening in the centre of the iris of the eye.
Etymology
The word "pupil" comes from the Latin word "pupilla", which means "little doll".
The first recorded use of the word "pupil" in English was in the 14th century.
Question
What happens to your pupil in a light room?
AQA Science Exam Question and Answer
Question:
Explain the function of the pupil in the human eye and how it responds to changes in light intensity.
Answer:
The pupil, a crucial component of the human eye, serves as the aperture that regulates the amount of light entering the eye. Its main function is to control the intensity of light reaching the retina, the light-sensitive layer at the back of the eye, which is essential for clear vision.
The pupil's diameter is controlled by the iris, a ring-like structure with muscles that can adjust its size. In response to changes in light intensity, the pupil's size changes to optimise vision. When the environment is bright, the circular muscles in the iris contract, causing the pupil to constrict or become smaller. This limits the amount of light entering the eye and prevents excessive light from overwhelming the retina.
Conversely, in dim lighting conditions, the radial muscles of the iris contract, causing the pupil to dilate or enlarge. This allows more light to enter the eye, enhancing the sensitivity of the retina to capture as much available light as possible for better low-light vision.
The dynamic adjustments of the pupil's size in response to changes in light intensity are part of the eye's automatic mechanisms that ensure optimal visual acuity in various lighting conditions. This coordinated action of the iris and pupil helps the eye adapt swiftly to changes in light and maintain clear and comfortable vision across a range of environments.