What controls the amount of light entering the eye?

Related questions

1. What's the most sensitive part of a female body?
2. What is the order in which light passes through the eye?
3. Why do images appear upside down on the retina?
4. What is the opening of the eye called?
5. What are the 3 tunics of the eye?
6. What is the top layer of the eye called?
7. How does light travel through the retina?
8. Which parts of the eye are most important when it comes to focusing light?
9. What is the difference between cornea and retina?
10. Does cornea protect eye?

Tags

1. #pupil
2. #entering
3. #opens
4. #closes
5. #control
6. #surrounding
7. #amount
8. #light
9. #enters
10. #tissue
11. #opening
12. #where
13. #black
14. #varies
15. #color
16. #pigmented
17. #appears
18. #looking
19. #center
20. #through