Final answer:
The harmonic frequency of a 2-meter long pipe open at both ends is the first harmonic, which is also considered the fundamental frequency.
Step-by-step explanation:
The student's question pertains to the harmonic frequency of a 2-meter long pipe that is open at both ends. The answer to what is its harmonic frequency is B) First harmonic.
In the context of physics and specifically acoustics, a harmonic is a frequency that is a multiple of the fundamental frequency. For a pipe that is open at both ends, the fundamental frequency is considered the first harmonic. Hence, the additional harmonics such as the second harmonic and third harmonic would be the next multiples of the fundamental frequency.
The terminology can sometimes be confusing because in some contexts, the term 'first overtone' is used interchangeably with 'second harmonic'. It's important to be aware that the nomenclature can vary, but the fundamental frequency always remains the first harmonic for a pipe open at both ends.