35 multiple-choice questions in College Board exam style. Each has four choices and a full explanation of why each option is right or wrong.
Don't confuse wave speed with particle speed. A common trap is assuming individual particles move as fast as the wave pattern itself.
For Doppler questions, think about crest spacing, not the wave "speeding up." The wave speed through the medium doesn't change: what changes is how frequently crests arrive.
For interference questions, identify path difference first. Whole wavelengths → bright/constructive; half wavelengths → dark/destructive.
Read the explanations even when you got it right. Each one teaches a small fact that often returns in a different form on the exam.