Radio waves and microwaves are similar because they both have
1 answer:
The correct answer is
b. low frequencies and low energy.
In fact, microwaves and radio waves have frequency up to , which are really low compared, for instance, to the frequency of gamma rays (
). Moreover, the energy of an electromagnetic wave is directly proportional to its frequency:
where h is the Planck constant and f the frequency; therefore, low frequency means also low energy.
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Frequency:
Explanation:
The force experienced by an electron in a magnetic field is
where
is the electron charge
v is the speed of the electron
B is the strength of the magnetic field
Since the force is perpendicular to the direction of motion of the electron, the force acts as centripetal force, so we can write:
where
r is the radius of the orbit
is the mass of the electron
Re-arranging the equation,
(1)
We also know that in a circular motion, the speed is equal to the ratio between circumference of the orbit and orbital period (T):
Substituting into (1),
We also know that 1/T is equal to the frequency f, so
In this problem,
Therefore, the frequency of the electrons is