Question

1. In a standing wave, the medium at the tip of a loop is
a) showing destructive interference
b) not moving
c) at the original amplitude of the wave
d) showing constructive interference

my answer: b

2. If a motorcycle is travelling toward an observer the frequency the observer hears is ___ the actual sound made by the motorcycle
a) greater than
b) lower than
c) smaller than
d) the same as

my answer: a

Answer 1

1. B, i agree with you
2. smaller than i think (b). the question is badly phrased.you hear a higher frequency (higher pitch) but an increased pitch is a shorter (smaller) wavelength. so technically the frequency is SHORTER, smaller would imply less amplitude (quieter)but i think it means what i said.
this is called the doppler effect

greater than implies either a gain of frequency (true when it is travelling away), or a higher volume/amplitude, which is simply not true so B

Answer 2

thanks a lot!

Answer 3

1) b
2) a

Answer 4

1)b
2) a, because closer he gets louder it sounds