<span>harnessing the sun's energy to produce heat or electricity is : Non-polluting
Unlike oil or gas based energy, solar energy create no dangerous emission that is dangerous for our environment.
Many scientist believed that solar energy is the answer to the environmental crisis that we currently faced.</span>
Answer:

Explanation:

where m is the mass, g is acceleration due to gravity
The masses m are on both sides hence they cancel

We know that T=2\pi W and substituting W with the above equation then

The answer is B. Hope I helped!
Answer:
the oscillations of the electrons must be in the 10⁸ Hz = 100 MHz range
Explanation:
The speed of a wave of radio, television, light, heat, all are manifestations of electromagnetic waves that are oscillations of electric and magnetic fields that support each other, the speed of all these waves is the same and the vacuum is equal to c = 3 108 m / s
All waves have a relationship between the speed of the wave, its frequency and wavelength
c = λ f
f = c /λ
for this case lam = 1 m
f = 3 10⁸/1
f = 3 10⁸ Hz
the oscillations of the electrons must be in the MHz range
It should be clarified that the speed of light in air is a little lower
n = c / v
v = c / n
the refractive index of vacuum is n = 1 and the refractive index of air is n = 1.000002
Money, or dictatiorship, trading, something that involes with money