Given a wave of a particular wavelength and amplitude, what must be the amplitude, wavelength, and phase change of a wave you add to this wave to create a wave of twice the amplitude? given a wave of a particular wavelength and amplitude, what must be the amplitude, wavelength, and phase change of a wave you add to this wave to create a wave of twice the amplitude?

The amplitude, wavelength and the phase of the second wave must be the same.

The waves will interact via constructive interference, which is possible only when the wavelength and phase of the waves are the same. During constructive interference, the waves overlap with one another to form a third wave with an amplitude equivalent to the sum of the amplitudes of the original waves.