Cellphones use radio frequency waves to transmit sound through the speaker and the microphone.<span> The radio frequency energy that is given off by cell phones is a type of electromagnetic energy.
I hope I helped! =D</span>
A. <span>I .................
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Answer:

Explanation:
As per thermal radiation we know that rate is heat radiation is given as

here we know that
T = 34 degree C = 307 K

e = 0.557


now we have




Answer:
2
Explanation:
To find force it's force = mass times acceleration so to find mass you would divide force by acceleration
Answer: Doppler Effect
Doppler Effect can be described as the change in
wavelength of a wave like upward shift in frequency for an object whom is
approaching and an apparent
downward shift in frequency for observers from whom the source is receding. This effect can be observed when a boat moves through the water then
the waves in front bunch up while the waves behind the boat spread out.