Does total internal reflection in an aquarium occur at the separation of the water and the glass or at the boundary of the glass and the water?
what is the difference between separation and boundary?
Total internal reflection occurs at the boundary between the water and the glass in an aquarium. To understand why this happens, we need to consider the phenomenon of refraction and the concept of the critical angle.
When light travels from one medium (such as air) to another (such as water or glass), it undergoes refraction, which means the light bends as it crosses the boundary between the two media. The amount of bending depends on the refractive indices of the two media. The refractive index is a measure of how much light slows down when passing through a medium.
In the case of water and glass, light travels slower in water than it does in air, and even slower in glass than in water. This means that as light enters water or glass from air or vice versa, it changes direction. This bending of light is what causes objects to appear shifted when viewed through a transparent medium.
Now, let's focus on the boundary between the water and the glass in an aquarium. When light passes from water into the glass, it bends towards the normal (the perpendicular line to the surface) because glass has a higher refractive index than water. This bending continues until a certain angle is reached, known as the critical angle.
The critical angle is the angle of incidence at which light is refracted at an angle of 90 degrees to the normal. If light strikes the boundary at an angle greater than the critical angle, instead of refracting, it undergoes total internal reflection. This means that all the light is reflected back into the same medium, and none of it is transmitted to the other side.
In the case of an aquarium, the critical angle is reached when light in water strikes the boundary with glass at an angle greater than the critical angle. At this point, total internal reflection occurs, and the light stays within the water rather than being transmitted into the glass. This is why we see the reflection of objects within the water, such as fish or plants, at the boundary between the water and the glass.
In summary, total internal reflection occurs at the boundary between the water and the glass in an aquarium when light in water strikes the glass at an angle greater than the critical angle.