The term mass is used to refer to the amount of matter in any given object For instance, a person or object may be weightless on the moon because of the lack of gravity but that same person or object maintains the same mass regardless of location
When two waves with different frequency travelling in the same medium meet each other, they produce an interference pattern called beat.
<em><u>The frequency of the beat produced is equivalent to </u></em><em><u>the difference between the individual frequencies of the two waves involved.</u></em>
<em><u>Therefore; in this case since the frequency of the beat is 20 Hz, that is from 20 beats per second.</u></em>
We need to find a pair from the choices whose frequency difference is 20 Hz.
This happens to be choice D. 22 Hz and 42 Hz, that is 42 Hz - 22 Hz = 20 Hz
Explanation: Group 18 is known as the Noble Gases. They are the most stable elements because they have a full outer shell of valence electrons, so they have no need to bond with other elements.
