Explain it

final-review — 3 short write-ups

Question 1 of 3

A checkpoint, not a test

Current and compass direction

A compass sits below a straight wire in a closed circuit. Explain why the compass deflects when the switch closes and predict what happens when the battery polarity is reversed.

Connect moving charge to a magnetic field, then use the direction of conventional current.

Question 2 of 3

A checkpoint, not a test

Connect a boundary to the wave equation

A light wave enters glass from air at an oblique angle (a nonzero angle to the normal). Explain why its wavelength becomes shorter even though its frequency does not change, and connect that change to the direction of refraction.

Combine n = c/v, v = fλ, and the higher index of glass.

Question 3 of 3

A checkpoint, not a test

Evidence for a hot early universe

Give two different observations that support the hot Big Bang model and explain what prediction each observation tests.

Choose from expansion and redshift, the cosmic microwave background, and primordial light elements.