Question

The eyes of amphibians such as frogs have a much flatter cornea but a more strongly curved (almost spherical) lens than do the eyes of air-dwelling mammals. In mammalian eyes, the shape (and therefore the focal length) of the lens changes to enable the eye to focus at different distances. In amphibian eyes, the shape of the lens doesn’t change. Amphibians focus on objects at different distances by using specialized muscles to move the lens closer to or farther from the retina, like the focusing mechanism of a camera. In air, most frogs are near-sighted; correcting the distance vision of a typical frog in air would require contact lenses with a power of about -6.0 D .Given that frogs are nearsighted in air, which statement is most likely to be true about their vision in water? (a) They are even more nearsighted; because water has a higher index of refraction than air, a frog’s ability to focus light increases in water. (b) They are less nearsighted, because the cornea is less effective at refracting light in water than in air. (c) Their vision is no different, because only structures that are internal to the eye can affect the eye’s ability to focus. (d) The images projected on the retina are no longer inverted, because the eye in water functions as a diverging lens rather than a converging lens.

Short answer

The correct answer is (b), They are less near-sighted because the cornea is less effective at refracting light in the water than in air.

Step-by-step solution

Define the refractive index.

The ratio of the speed of light in a vacuum and velocity in a specified medium is known as the refractive index.

Determine the true statement.

Since the refractive index of air is less than the refractive index of water and the refractive index of water is closer to the refractive index of the cornea of the frogs. Therefore, the vision of frogs becomes better in the water than in the air.

Hence, they are less nearsighted, because the cornea is less effective at refracting light in the water than in air.