Semicolon or period in the following? [duplicate]

Question

Here are two instances in a formal paper I submitted where my professor told me my semicolon usage is incorrect. He says that, in both instances, a period should be used. Is he right? I maintain that I've used them appropriately and at my discretion to indicate closeness of subject matter between two independent clauses.

Instance 1:

Baz Luhrmann, in his 2013 film adaptation of Fitzgerald’s work by the same name, represents its major characters in a manner mostly true to the novel; Nick, Gatsby, Daisy and Tom are somewhat polarized, however, in their speech and actions.

Instance 2:

In the novel, when Nick is “urged” (28) by Myrtle to go along, bribed with the promise of Myrtle’s sister, he responds “Well, I’d like to, but—” (28); in the film, he worriedly says, “No, no, no—that’s alright.”

Answer 1

The short answer is that, yes, your usage is correct.

For more information, I refer to the ever humorous Oatmeal: http://theoatmeal.com/comics/semicolon

(And for the serious readers, I refer to this excellent answer about however: Use of a semicolon before and comma after "however")

As an aside, I think putting however at the beginning of the second independent clause in the first sentence would make it stronger. Something like:

Baz Luhrmann, in his 2013 film adaptation of Fitzgerald’s work by the same name, represents its major characters in a manner mostly true to the novel; however, Nick, Gatsby, Daisy and Tom are somewhat polarized in their speech and actions.