A light ray is travelling from air medium to water medium (refractive index = 1.3) such that angle of incidence is x degree and angle of refraction is y degree. The value of ratio (sin y)(sin x) is:

​​The correct answer is:B. 1/1.3

This problem deals with Snell's Law of Refraction, which states that:

​$$\frac{\sin x}{\sin y} = \frac{n_2}{n_1}$$​​

Where:

x is the angle of incidence (in the air),

y is the angle of refraction (in water),

$$n_1$$​ is the refractive index of air, which is approximately 1,

$$n_2$$​ is the refractive index of water, which is given as 1.3.

Using Snell's Law:

                                  $$\frac{\sin x}{\sin y} = \frac{1.3}{1}$$

                             $$sin⁡x=1.3siny$$​​​

Now, the given ratio to calculate is (sin y)(sin x):

​$$sin⁡x⋅sin⁡y=(1.3sin⁡y)⋅sin⁡y=1.3sin⁡2y\sin x$$​​

But we also know that $$sin⁡x=1.3sin⁡y$$  so the value of the ratio$$\sin x / \sin y$$ is​

​$$\frac{\sin x}{\sin y} = \frac{1.3}{1}$$​​

Thus, the correct ratio value is:

​$${ \frac{1}{1.3} }$$​​​​​