In the diagram above, if the south poles of two magnets stroke a steel bar, the polarities at X and Y will respectively be

Which of the following types of electromagnetic waves is used in night vision goggles?

Which of the following is a type of wave that is both mechanical and longitudinal?

In an AC circuit, resonance occurs when the impedance of the circuit is:

The pitch of a musical note is determined by the frequency of the sound wave that it produces. If two instruments have the same frequency, which of the following factors will most affect the difference in their pitches?