Answer:

<h3>B. Speed at which it leaves the ground</h3>
Answer:0.27*10^{6} (m)
Explanation:
with a wave we know that speed= wavelenght* frecuency so
wavelenght= 3*10^{7} / 109 = 0.27*10^{6} (m)
Answer:
a

b

Explanation:
From the question we are told that
The wavelength is 
The energy is 
This energy is mathematically represented as

Where c is the speed of light with a value 
h is the Planck's constant with the value 
n is the number of pulses
So

substituting values


Given that the pulses where emitted 20 times in one second then the period of the pulse is


Hence the average power of photons in one 80-mJ pulse during 1 s is mathematically represented as

substituting values


Hello,
Here is your answer:
The proper answer to this question will be option A "An accelerating electric point charge (electron) emits electromagnetic waves." That's because electromagnetic waves are formed by motion of electrically charged particles (electrons)!
Your answer is A!
If you need anymore help feel free to ask me!
Hope this helps!