Video Transcript
Which of the following particles
have a relative charge with a magnitude of one-third? Proton, bottom antiquark, top
antiquark, bottom quark, down quark, up antiquark, strange antiquark.
All right, so we’re looking for all
the particles in this given list with a charge magnitude of one-third. We can see that this is a
fractional charge. And that is the hallmark of a quark
or an antiquark. Looking at our list, we see all of
the choices fall under this description except one. The proton, the first item listed,
has a relative charge of positive one. Right away then, we see that we can
cross off this answer choice.
So now, let’s look at the quark and
antiquark types listed. As we do, one important thing to
keep in mind is that we’re looking for particles that have a relative charge
magnitude of one-third. This means that any particle with a
charge of plus or minus one-third fits this description. To get started answering this
question, let’s recall the six types of quark. By pairs, there are the up and down
quark, the charm and strange quark, and the top and bottom quark. When they’re written out like this,
we know that all the quark types in our top row have the same relative charge,
positive two-thirds. And likewise, all the types of
quark in our bottom row have the same relative charge, negative one-third.
Recalling that we’re looking for
particles that have a charge magnitude of one-third, we can see that the magnitude
of this relative charge, negative one-third, is positive one-third. And therefore, any down, strange,
or bottom quarks we see on our list qualify. Looking once more at our answer
options, we see the bottom quark and the down quark listed here. And so, we know those are particles
that do have a relative charge with a magnitude of one-third. And now, let’s look at the
remaining particles, which are all antiquarks.
Just like with the quark types, we
can write out the antiquark types according to their pairs. And now, the types in the top row
have a relative charge of negative two-thirds and those in the bottom have a
relative charge of positive one-third. This means that if we find the down
antiquark, the strange antiquark, or the bottom antiquark in our list, then those
satisfy the condition we’re looking for. And indeed, we see the bottom
antiquark here and the strange antiquark here. The other two choices, the top and
the up antiquark, do not have the relative charge we want. So, we can cross out those options
and then select as part of our answer the bottom and strange antiquarks. So, of the particles in our
original list, the bottom antiquark, the bottom quark, the down quark, and the
strange antiquark, all have a relative charge with a magnitude of one-third.
