91影视

Snell's Law: It relates the refraction angle ${胃}_2$to the incident angle${胃}_1$and the indexes of refraction of the incident medium n1 and the refracted medium n2

$n_1\sin 鈦�{胃}_1=n_2\sin 鈦�{胃}_2$

Angles of incidence and refraction are measured with respect to the normal line at the point where the ray intersects the interface between the two media. Medium 2 is more optically dense (has a higher refractive index) than medium 1 if the refracted ray is closer to the normal than the incident ray. In the same plane are the incident ray, refracted ray, and normal line.

A fish in an aquarium looks out at a cat.

The index of refraction of air is $1.00$.

The index of refraction of water is $1.33$

We are asked to determine whether the cat's apparent distance is less than, equal to, or greater than its actual distance to the fish.

Consider the paraxial rays that refract from the air into the water and consider the cat to be a point source. Because water has a higher index of refraction than air, the cat's rays are refracted toward the normal at the surface and diverge outward. Extending the outgoing rays backwards results in an image of the cat that is further away from the aquarium than it actually is.

As a result, the distance to the cat appears to be greater than it is.