True or False

1. The frequency of the wave can be changed by changing the frequency at which the waves are generated

2. Two crests are out of phase with each other. A crest and a trough are in phase with eachother

3. When a wave reaches the boundary of a new medium, part of the wave can be reflected and part of the wave can be transmitted into the new medium

My work
I think
1. False
2. Flase
3. True

3 answers

1. sure, whistle different notes.

2. I agree false.

3. I agree true.
So for 1. Am i right is it false?
I think 1 is true. I can change the frequency of the sound waves from my lips by changing the frequency I generate them at. In fact the wave frequency is the generator frequency.