"Othello" - William Shakespeare (Act IV)

ACT IV
1. Iago deceives Othello even further, by having him overhear the conversation with Cassio. Also, the handkerchief plays a major role in this act - when Othello sees Bianca give it to Cassio, he becomes quite convinced of Desedemona's infidelity.
2. It is not terribly plausible, but we have to remember that Iago is a master planner. While he may not have planned for that particular event to occur, he set the stage so that, no matter what did occur, things would look questionable to Othello, as he looked on. The handkerchief is very important to the play. To Othello, it represents both the part of his heart his has given to Desdemona, and her own purity and faithfulness to him. She, on the other hand, sees it more as simply a handkerchief, a gift. Iago plays on Othello's stronger attachment to the handkerchief to achieve his ends. It also seems to carry with it some sort of mystical, magic-like connotations for Othello. This only adds to the importance of it in his mind.
3. He is already convinced that she is unfaithful, and I don't believe that much of anything would change his mind at this point. She defends herself as best she can, although he has not given her all the information about what his claims are, or how he has come to them. This is one of those moments in the play when we see that communication would have been vital, and could have caused everything to be cleared up in an instant. But Othello chooses to hold fast to his forming opinions, and her protests fall on deaf ears.
4. He uses his anger against him, and turns it onto Cassio. This both serves to protect himself, and get someone else to deal with Cassio, so his hands can be "clean" persay.
5. I answered this one with an in-class essay, so I shall omit it. :)

Quotes:
Desdemona: "Wouldst thou do such a deed for all the world?"
Emilia: "The world's a huge thing. It is a great price for a small vice."

"Good night, good night. God me such uses send not to pick bad from bad, but by bad mend!"
- Desdemona