After a beam of UV light with the wavelength of 300 nm in the vacuum travels from vacuum into a glass, its wavelength changes to 250 nm. What is the refractive index of this glass for this light beam? Please keep 2 significant figures.

1.2    

Explanation:

First find the frequency of UV light as follows:

The frequency does not change when light enters from vacuum into glass.

Refractive index of glass can be calculated as follows:

where, v is the velocity of UV light in glass.

the answer is b i think