Question: A fish is swimming 2m below the surface of a calm lake. At what angle to the horizontal must the fish look to observe a fisherman sitting ~ 50 m away at the edge of a lake ( the refractive index n= 1.33 for water). Solution: In this case the way the fish can see horizontally across the lake is when the angle of incidence is nearly 90 degrees in the air. This corresponds to the light ray inside the water being refracted close to the critical angle for total internal reflection where sin θc = 1/n, giving θ = 48.6 degrees. This is with respect to the normal, so the horizontal angle the fish needs to be looking at is 41.4 degrees. Here, I understand the critical angle is 48.6 degree. However, what does it mean by "This is with respect to the normal, so the horizontal angle the fish needs to be looking at is 41.4 degrees." ?
Refraction of Light
Refraction is a change in the direction of light rays when they travel from one medium to another. It is the bending of light when it goes through different media.
Angle of Refraction
Light is considered by many scientists to have dual nature, both particle nature and wave nature. First, Particle nature is one in which we consider a stream of packets of energy called photons. Second, Wave nature is considering light as electromagnetic radiation whereas part of it is perceived by humans. Visible spectrum defined by humans lies in a range of 400 to 700 nm wavelengths.
Index of Refraction of Diamond
Diamond, the world’s hardest naturally occurring material and mineral known, is a solid form of the element carbon. The atoms are arranged in a crystal structure called diamond cubic. They exist in a huge variety of colours. Also, they are one of the best conductors of heat and have a very high melting point.
Question: A fish is swimming 2m below the surface of a calm lake. At what angle to the horizontal must the fish look to observe a fisherman sitting ~ 50 m away at the edge of a lake ( the refractive index n= 1.33 for water).
Solution: In this case the way the fish can see horizontally across the lake is when the angle of incidence is nearly 90 degrees in the air. This corresponds to the light ray inside the water being refracted close to the critical angle for total internal reflection where sin θc = 1/n, giving θ = 48.6 degrees. This is with respect to the normal, so the horizontal angle the fish needs to be looking at is 41.4 degrees.
Here, I understand the critical angle is 48.6 degree. However, what does it mean by "This is with respect to the normal, so the horizontal angle the fish needs to be looking at is 41.4 degrees." ?
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