standing waves

Question 1

what is it called when you add two waves together by adding their amplitudes at all points?

Answer 1

superposition

Question 2

explain standing/stationary waves

Answer 2

when you have 
two waves of the same frequency 
of similar amplitude
travelling in opposite directions
they superpose
to create standing/stationary waves

Question 3

what are nodes?

Answer 3

points where a wave cross the x-axis

Question 4

what are antinodes

Answer 4

points of amplitude, max height above the x-axis

Question 5

what is the formula for the nth harmonic

Answer 5

l = nlambda/2