4. What is the frequency of an electromagnetic wave with a wavelength
of 20 m?

The frequency of radio waves with a wavelength of 20m is

1.5 e+7 Hertz (Hz) or 15 million Hertz.

This was obtained from the formula speed (c) is equal to the product of frequency (f) and wavelength (λ)

c = fλ  

Since we are looking for the frequency, we will divide both sides of the formula above by the lamda symbol for wavelength, which gives us:

f = c / λ

The value of wavelength is already given which is 20 meters. The speed of radio waves is the same with the speed of light when travelling in a vacuum – also with the other electromagnetic waves. Hence the speed (c) is 3 e+8 m/s

f = 3 e+8 m/s   /    20m

f = 1.5 e+7 H

Explanation:

this is the correct answer you want.

explanation: in any substance/object, the particles inside it (atoms/molecules) constantly move in random directions and with random speeds (this motion is called brownian motion). as a result, the particles have some kinetic energy (which is proportional to the temperature of the substance).

explanation:

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b) phosphorus pentoxide