Determine the inductance L of a 0.65-m-long air-filled solenoid 3.2 cm in diameter containing 8400 loops.

The inductance is  

Explanation:

From the question we are told that

  The  length is  

   The  diameter is  

    The  number of loops is  

Generally the radius is evaluated as

The  inductance is mathematically represented as

Here is the permeability of free space with value  

A is the cross-sectional area which is mathematically evaluated as

=>        

=>        

 =>  

=>    

wavelength divides in half and speed stays the same.