In gamma ray emission from a nucleus :

Frequencies of various radiations are given as

$f_V\to$ Visible light

$f_R\to$ Radio waves

$f_{UV}\to$ Ultra violet waves

Then which of following is true?

Which layer in the atmosphere protects us from ultraviolet rays?

Consider the following
(i) Submarine communications
(ii) A.M. radio
(iii) Shortwave ratio
(iv) Radar

Arrange the above in increasing frequency of the waves associated with them