Chapter 22 - Reflection and Refraction of Light - Learning Path Questions and Exercises - Exercises - Page 774: 21

Wavelength $=140.26nm$ Frequency $=1.55\times10^{15}Hz$

Required wavelength $=\frac{lambda_{air}}{n}=\frac{193nm}{1.376}=140.26nm$ Frequency of light does not change in the medium. So, required frequency =$\frac{c}{lambda_{air}}=\frac{3\times10^{8}}{193\times10^{-9}}=1.55\times10^{15} Hz$