Exploring Refraction

My sister bought two plakat (shortfin)  betta fish. They are combination of white and blue. They  are beautiful especially their tails as they swim in the water. Before she transfered them in the fish tank. I took a video of how they looked  

https://www.youtube.com/shorts/RkVySiJtn-Y

As you can see when the fish swam above the water it is in the same size but when it swam underwater, it became larger. Why is it so?

In the water, the fish is the same size. Its apparent size, however, varies. Due to light refraction, the size appears to be larger underwater. When the eye is close to the surface of the water, objects in the water that are seen through a flat surface do appear magnified. This is common knowledge for anyone who has ever used a diving mask underwater. 

The light rays coming from the two ends of the object will be refracted in the same way and according to Snell's law by the water's flat surface. When discussing light or other waves flowing through a border between two different isotropic media, such as water, glass, or air, Snell's law is a formula used to describe the relationship between the angles of incidence and refraction. A little thing may only appear to be raised up if you look at it vertically from the top and it is horizontal, but the object's length should remain constant. This is due to the fact that we are catching nearly parallel to normal rays.

Light passes through air  in a straight line. But as it passes through the water the light can't travel quickly as it is through air.  So basically the light refraction gives the fish a magnifying effect which makes the angle appear bigger than it actually is. 

Now my sister has transfered her fish in the  fish tank. 

Try this experiment at home. 

What you need: 

Pencil, glass of water

Procedure:

Place the pencil in the glass holding straight up and down ( not at an angle). Take a picture. What do you notice? 

The pencil appears straight when viewed through the side of the glass. 

Fill the glass 2/3 full of water. Take the pencil and let it lean againts the side of the glass. Take another picture and be sure not to change the position or angle relative to the object. 

Compare the two pictures. Notice that when you look through the glass at the pencil. Notice that it appears bent. This is the effect of refraction or bending of light.

Explanation: 

Does this mean that everything we view through our clear glass windows is actually distorted and not in the position that it appears to be if light is bent when travelling through a transparent material? Yes and no, Refraction does happen, but the result of the bent light cancels out in the end. It's important to keep in mind that light can pass through both the inside and outside sides of a clear glass. The path of the light is bent in one direction when it enters through the inside surface of the glass, and it is bent in the opposite direction when it leaves through the outside surface, canceling out the impact of refraction.Everything looks to be exactly where it is positioned.