Two identical waves, each of intensity 1.00 W/m squared, interfere perfectly constructively. What is the intensity of the resulting wave?

1. Perfect constructive interference of two identical waves of amplitude X gives a wave of amplitude 2X. 2. Intensity is proportional to amplitude squared. 3. So the new intensity is proportional to (2X) squared = 4 X squared, four times the old value. 4. Taking the ratio, the new intensity divided by the old is 4. 5. New intensity = 4 x 1.00 W/m squared = 4.00 W/m squared. 6. Answering 2.00 W/m squared adds the intensities, which works for amplitudes but not for their squares. 7. Zero would be the result of perfectly destructive interference instead. _Source: OpenStax College Physics (CC BY 4.0), Ch 16 "Oscillatory Motion and Waves", section 16.11 Energy in Waves: Intensity_