Critical Thinking Items
16.3 Lenses
When you focus a camera, you adjust the distance of the lens from the film. If the camera lens acts like a thin lens, why can it not be kept at a fixed distance from the film for both near and distant objects?
- To focus on a distant object, you need to increase the image distance.
- To focus on a distant object, you need to increase the focal length of the lens.
- To focus on a distant object, you need to decrease the focal length of the lens.
- To focus on a distant object, you may need to increase or decrease the focal length of the lens.
Part A—How do the refractive indices of the cornea, aqueous humor, and the lens of the eye compare with the refractive index of air?
Part B—How do the comparisons in part A explain how images are focused on the retina?
- (A) The cornea, aqueous humor, and lens of the eye have smaller refractive indices than air.
(B) Rays entering the eye are refracted away from the central axis, which causes them to meet at the focal point on the retina. - (A) The cornea, aqueous humor, and lens of the eye have greater refractive indices than air.
(B) Rays entering the eye are refracted away from the central axis, which causes them to meet at the focal point on the retina. - (A) The cornea, aqueous humor, and lens of the eye have smaller refractive indices than air.
(B) Rays entering the eye are refracted toward the central axis, which causes them to meet at the focal point on the retina. - (A) The cornea, aqueous humor, and lens of the eye have greater refractive indices than air.
(B) Rays entering the eye are refracted toward the central axis, which causes them to meet at the focal point on the retina.