Question

redshift and blueshift quick check
which situations might cause two observers (a and b) to measure different frequencies for the same vibrating object? select the two correct answers. (1 point)

• observer a is stationary and observer b is moving
• observer a and observer b are both stationary and at the same distance from the object
• observer a and observer b are stationary but at different distances from the vibrating object
• observer a and observer b are moving at different speeds relative to each other

Explanation:

The Doppler effect causes frequency changes due to relative motion (not distance). So:

• "Observer A is stationary and Observer B is moving": Motion difference causes frequency change.
• "Observer A and Observer B are moving at different speeds relative to each other": Different relative speeds cause frequency difference.
• The other options involve distance (stationary at same/different distances), which doesn't affect frequency (Doppler effect is about motion, not distance).

Answer:

• Observer A is stationary and Observer B is moving
• Observer A and Observer B are moving at different speeds relative to each other