I don't understand passive voice [closed]

So... Here is first phrase from "TBBT":

So if a photon is directed through a plane with two slits in it and either slit is observed, it will not go through both slits.

I'm confused with this part "a photon is directed". Can I say other way "Somebody directed a photon through a plane"? Are these variants same?

Solution 1:

In the realms of math and science, we tend to use a passive voice. From Purdue:

Also, writers in the sciences conventionally use passive voice more often than writers in other discourses. Passive voice makes sense when the agent performing the action is obvious, unimportant, or unknown or when a writer wishes to postpone mentioning the agent until the last part of the sentence or to avoid mentioning the agent at all. The passive voice is effective in such circumstances because it highlights the action and what is acted upon rather than the agent performing the action.

You could of course say If someone directs a photon through a plane..., but then it sounds like photons have special properties if humans are involved and the whole exercise takes away from the actual point, which doesn't rely on us silly humans at all.