The correct option is (c).
Explanation
The human eye functions as a natural optical instrument. It comprises a lens system (cornea and crystalline lens) that focuses light onto the retina, while the iris acts as a variable aperture to control the intensity of light entering the eye.- Statement 1 is Incorrect: The iris is the pigmented, muscular diaphragm located behind the cornea. It is the iris that contains melanin and gives the eye its distinctive colour (e.g., blue, brown, or green). The cornea is a transparent, convex outer layer responsible for the initial refraction of light.
- Statement 2 is Correct: The pupil is the central aperture within the iris. It appears black because the light entering through it is absorbed by the internal tissues of the eye (specifically the retina and choroid) and is not reflected back out through the opening.
- Statement 3 is Correct: The iris regulates the amount of light entering the eye by adjusting the diameter of the pupil. In bright light, the circular muscles of the iris contract, causing the pupil to constrict (become smaller). This reduces the amount of light entering the eye to protect the retina.
Key Takeaway: The iris determines eye colour and controls the pupil size to regulate light intensity. The pupil appears black due to the absorption of light, and the cornea acts as the transparent window for light entry and refraction.