Question

Study the following incident.
Swara and Yash were looking in a water filled vessel. They could see their images clearly in the still water. At that instant, Yash threw a stone in the water. Now their images were blurred. Swara could not understand the reason for the blurring of the images.
Explain the reason for blurring of the images to swara by answering the following question.
Which types of reflection of light can you notice from this?

Answer 1

Hint: In case of mirrors usually there are three types used. Plain mirror, concave mirror and convex mirror. All will serve different purposes. Properties of different mirrors are different. In case of convex mirrors they always form virtual images. While concave mirrors form both virtual and real images and we will see about plain mirrors.
Formula used:
$\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$

Complete answer:
Before discussing why blur images are formed, we should discuss types of mirrors, mainly plain mirror because the answer is related to properties of plain mirror.
In case of convex or concave mirrors the focal length of the mirror determines the type and size of the image formed. Same with the case of plane mirrors also.
$\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$ This is the mirror formula
Where v is the image distance while u is the object distance and f is the focal length.
But here the focal length of the plane mirror will be infinity. Mathematically the inverse of infinity will be zero. From the above formula we get
$v = - u$
If we consider only the magnitude distance of the object from the mirror will be equal to the distance of image from the mirror and magnification of the mirror will be $\dfrac{{ - v}}{u}$ which is one in this case and it is positive.
Hence if magnification is positive then image formed will be erected and rule is when only one mirror is present and image formed is erected then that image must be virtual.
Hence an image formed by a plane mirror is always virtually erect and laterally inverted.

In the above image formed due to the plane mirror it is laterally inverted i.e left portion of object becomes right side portion for the mirror.
So initially still water behaves as a plain mirror and all the above properties we had told are applicable for images of swara and yash. The kind of reflection is regular reflection as the water is still. All the rays which are reflected from surface reaches eyes of both
When stone is thrown, the surface will become irregular due to ripples and reflection will be irregular and only some reflected rays will reach the eyes of both and hence the image formed will be a blurred image.

Note:
 In both the cases, the rays coming from swara’s and yash’s body will get reflected on the surface and reach the eyes of both. In both the cases, whether the surface is regular or the surface is irregular, laws of reflection are followed in both the cases. The sizes of the images will be the same.