Final answer:
The statement that the amplitudes of waves add up only when they are propagating in the same line is true, and it applies to the concept of wave interference. Electromagnetic waves, such as light, always propagate at a constant speed in a vacuum, independent of their frequency, and their electric and magnetic fields are mutually perpendicular to their direction of propagation.
Step-by-step explanation:
The question regarding the propagation of waves involves understanding the relationship between wave velocity, wave frequency, and wavelength. It's important to note that the speed of propagation in a given medium is constant for all waves of the same type, such as all sound waves in air or all light waves in a vacuum.
The statement about the amplitudes of waves adding up is true only if they are propagating along the same line. In wave interference, when two waves meet while traveling along the same line, their amplitudes combine algebraically, which is known as constructive or destructive interference depending on their phase relation.
Electromagnetic waves, which include light waves, have unique properties like the mutually perpendicular directions of the electric field (E), magnetic field (B), and wave propagation, and they can travel through a vacuum at a speed c, which is independent of frequency.
The amplitude addition question (question 42) has its answer in the idea that two waves will only add their amplitudes if they are propagating along the same line in the same or opposite directions. Lastly, the speed of wave propagation is dependent on the medium and not directly on the frequency or wavelength, though these two are inversely related given the constant speed in a particular medium.