Question

explain = Maximum usable frequency

Answer 1

the frequency which is widely used in our daily lives mark me as brainlist

Answer 2

Heya......!!!!

It is the Highest frequency of radio waves which when sent at some angle towards the ionosphere , gets reflected from that and return Earth .

Quantitatively , MUF =>>
$\frac{n}{ \cos(i) } = \sec(i) \times n$

Here , i is thr angle between normal and the direction of incidence waves .

Hope it helps u ^_^