Question

Lemon in the water of a glass tumbler appears bigger that it’s actual size, when viewed from the sides of tumblr because
(A) Rays of light travelling from denser to rarer medium travel away from normal
(B) Rays of light travelling from denser to rarer medium travel towards normal
(C) Rays of light travelling from rarer to denser medium travel away from normal
(D) Rays of light travelling from rarer to denser medium travel towards normal

Answer 1

When the light travels from one transparent medium to another transparent medium, the process is known as Refraction. During refraction the frequency of light rays remains constant.

Complete step by step answer:
Refraction is defined as the process in which light rays travel from one transparent medium to another transparent medium. During this process the frequency of the light rays remain constant. So we know that,
$c = \nu \lambda$
$\Rightarrow \nu = \dfrac{c}{\lambda }$
Where, $c =$Speed of light
$\nu =$Frequency of light
$\lambda =$Wavelength of light
This means that for frequency to be constant, during refraction the velocity and wavelength of light changes.
Now there are two types of transparent media, the rarer medium and the denser medium. The refractive index in the rarer medium is less than the refractive index in the denser medium. Basically, the molecules in the denser medium are more compactly packed than the rarer medium. Now the concept of rarer and denser media is completely relative. Which means that a medium can be denser when compared to one medium but be rarer for another medium. For example, when compared with air, water is considered to be a denser medium but when compared with glass, water turns out to be the rarer medium.
Since, the molecules are more compactly packed in the denser medium, the velocity of light decreases in the denser medium. That is, when light travels from rarer to denser medium the velocity of light decreases. And because of this, light tends to deflect towards the normal. Which means that when traveling from rarer to denser medium, light moves towards the normal, and the vice-versa.
Now, in this case the light rays coming from the lemon first travel from water to glass, that is from rarer medium to denser medium. So the light rays move towards the normal. Then, the light travels from glass to air, that is from denser medium to rarer medium. So the light rays move away from the normal. But since, the difference between the refractive indices of glass and air is greater than the difference between the refractive indices of water and glass. So, as a result the light moves away from the normal. Which means that the light appears to be slightly away from where it should have been. And that’s why the lemon appears to be slightly bigger than it is supposed to be.

Now, out of the four options, options A and D are factually correct. But for this instance, option A is more correct answer.

Note: Refractive index is actually the ratio between the velocities of light in the two different media. Relative refractive index is when we compare the velocity of light in any two different medials. But the absolute refractive index is when we compare the velocity of light in one medium to that of the velocity of light in air.