Final answer:
The statement that amplitudes of waves only add up when propagating in the same line is false due to the concept of interference. James Clerk Maxwell, not André-Marie Ampère, was key in developing the theory of electromagnetic waves with his Maxwell's equations. Also, the photoelectric effect is not exclusive to visible light.
Step-by-step explanation:
The statement that amplitudes of waves add up only if they are propagating in the same line is false. When two or more waves meet, they interfere with each other; the amplitudes may combine constructively or destructively, regardless of whether they are propagating in the same line or not. This phenomenon of waves affecting each other is known as interference.
James Clerk Maxwell is the physicist who greatly contributed to the electromagnetic wave theory. His formulation of Maxwell's equations provided a complete and symmetric theory of electricity and magnetism, predicting that visible light is a form of electromagnetic waves. It's notable that the question references André-Marie Ampère, who also made significant contributions to the field of electromagnetism, but it was Maxwell who predicted electromagnetic waves.
Moreover, to clarify a related concept, it's false that visible light is the only type of electromagnetic radiation that can cause the photoelectric effect; other forms of electromagnetic radiation can also cause this effect.