Wave speed = (wavelength) x (frequency)
= (4 m) x (2 /sec)
= 8 m/sec
Solution :
a). Using Gauss's law :
,
.........(1)
Let
in equation (1)
Therefore,
.............(2)



....................(3)
Therefore, 

.............(4)
Now differentiating the equation (4) w.r.t. 'b', we get
Thus the radius for the inner cylinder conductor is 
b). For the energy storage, substitute the radius in (4), we get

This is the amount of energy stored in the conductor.
Answer:
1. Molecular cloud
2. Close binary
3. Brown dwarf
4. Protostellar wind
5. Thermal pressure
6. Protostellar disk
7. Jet
8. Degeneracy pressure
Explanation:
1. The Sun formed, probably along with other stars, within a large molecular cloud.
2. A Close binary consists of two stars that orbit each other every few days.
3. A Brown dwarf is a "star" so small in mass that its core never gets hot enough to sustain nuclear fusion reactions.
4. Most of the gas remaining from the process of star formation is swept into interstellar space by a protostellar wind.
5. As a protostar's internal temperature increases, its growing thermal pressure helps slow its contraction due to gravity.
6. Planets may form within the protostellar disk that surrounds a forming star.
7. Mass can be lost through a jet of material ejected along a protostar's axis of rotation.
8. A "star" with mass below 0.08 solar mass has its gravitational contraction halted by degeneracy pressure.
The answer is flight technology, satelite technology, and exploration technology.
The flight technology include advances in jet propulsion and navigation. Satelite have become more and more powerful and hecne communication with distant objects is increasing in efficiency. The emergence of AI robots in space exploration are reducing risks to humans in these deep ventures.