what the amplitude of the resulting wave is when a +10 cm wave encounters a +20 cm wave, and when a +10 cm wave encounters a -20 cm wave? Do you add them like positives and negatives/ positives and positives,

Vasantha Kumari
askIITians Faculty 38 Points
8 years ago

Let us first recall these two ways of interference:

Constructive Interference: If two waves both have positive amplitudes meet and with equal amplitude their resulting amplitude is twice of either of individual waves.(your ex.. +10 cm and +20 cm wave.

Destructive Interference: If two waves but one with positive amplitude meets another amplitude with negative value then their resulting amplitude will be smaller than either of individual waves.(your ex.. +10 cm and –20 cm wave)

And as you rightly said the overall displacement of the wave is as easy with simple arithmetic:

 Displacement of Pulse 1 Displacement of Pulse 2 = Resulting Displacement +1 +1 = +2 -1 -1 = -2 +1 -1 = 0 +1 -2 = -1

Tip: you could also estimate the position between the various marked points and sketching the wave.( green line in the figure as shown)

Thanks & Regards,

Vasantha Sivaraj,

TEJKIRAT SINGH
65 Points
7 years ago

Constructive
Interference:

If two waves both have positive amplitudes meet and with equal amplitude their
resulting amplitude is twice of either of individual waves.(your ex.. +10 cm
and +20 cm wave.
Destructive
Interference:

If two waves but one with positive amplitude meets another amplitude with
negative value then their resulting amplitude will be smaller than either of
individual waves.(your ex.. +10 cm and –20