Question

Give reason: The bottom of the water tank appears raised.

Answer 1

Hint: We all know that the image that we see comes from the mirror reflection. The image appears to come from inside the mirror at a hypothetical point. The image formed in a plane mirror is generally erect and laterally inverted, the condition being the object is if not symmetric.


Complete step by step answer:
When light travels from one medium to the other medium, it changes its path due to the difference of densities in the two mediums. A convention term called refractive index relates the refraction of light from one medium to the other medium.

When light travels from water to air, it bends towards the normal and we get a wrong perception of the image of the bottom of the water surface getting raised.
Additional information: One of the applications of refraction is the phenomenon of Total internal reflection. TIR is defined as when a ray of light travelling from denser to a rarer medium is sent back to the same denser medium if it strikes the interface of the rarer-denser medium at an angle greater than the critical angle. It has two necessary conditions:
i) The light must travel from denser to rarer.
ii) The angle of incidence must be greater than the critical angle.



Note: The definition of the refractive index can also be told as the ratio of the speed of light in vacuum to the speed of light in another medium may be water, glass etc. and it is represented as:
$\mu = \dfrac{c}{v}$
Here, $\mu $ is the refractive index, c is the speed of light in vacuum and v is the speed of light