21.
The ratio of the total solar radiant energy returned by a planetary body to the total radiant energy incident on the body, the called:

22.
Which one of the following parameters is accurate for DGPS?

24.
If electric permittivity and magnetic permeability of the medium are respectively $$\varepsilon $$ and $$\mu $$, then the velocity (Cm) of the electromagnetic wave in the medium is given by:

26.
Which one of the following statements is correct regarding the GPS satellites?