Took plan b after/during ovulation. will it work?

Hopefully: Plan b works most effectively when taken immediately after unprotected intercourse. And it's mechanism is to prevent ovulation. That's if you've already ovulated, Plan B is not very effective at preventing pregnancy. The Progesterone in Plan B can make the environment for sperm less hospitable, but for prevention of pregnancy it's very limited.

Agree w Dr Van Dis: Plan B One-Step is up to 89 % effective when taken within 72 hours (3 days) after unprotected sex. It can reduce chance of pregnancy by up to 95% if used within 24 hours. It continues to reduce the risk of pregnancy up to 120 hours (5 days) after unprotected sex, but is less effective as time passes. It can be taken at any time during the menstrual cycle.