The waves that are bent down by the ionosphere are

The wave that are bent down by the ionsphere on are

Among the following the waves which can penetrate the ionosphere are

Among the follwing , the waves which can penetrate the ionosphere are

If f c is the critical frequency of radio waves for reflection by the ionosphere and N max is the density of free electrons in the ionosphere

Long range radio transmission is possible when the radio waves are reflected from the ionosphere. For this to happen the frequency of the radio waves must be in the range: