The pitch of sound depends upon the frequency of the sound by the emitting source. Greater the frequency of the sound , higher will be the pitch of that sound.

Introduction:
The pitch of sound refers to the perception of how high or low a sound is. It is determined by the frequency of the sound wave. The frequency of a sound wave refers to the number of complete vibrations or cycles that occur in a given unit of time. Pitch is a subjective perception that varies from person to person.

Explanation:
The correct answer is option 'D', which states that the pitch of sound depends on frequency. Here's an explanation of why frequency is the correct answer:

Frequency:
- Sound waves consist of compressions and rarefactions that propagate through a medium, such as air or water. These waves are characterized by their frequency, which is the number of complete vibrations or cycles that occur in a given unit of time.
- Frequency is usually measured in hertz (Hz), which represents the number of cycles per second. For example, if a sound wave completes 200 cycles in one second, its frequency is 200 Hz.
- Higher frequency sound waves have more cycles per second, making them perceive as higher-pitched sounds. On the other hand, lower frequency sound waves have fewer cycles per second, resulting in lower-pitched sounds.
- Humans can typically hear sounds with frequencies ranging from 20 Hz to 20,000 Hz. Frequencies below this range are referred to as infrasound, while frequencies above this range are called ultrasound.

Relation to Pitch:
- The pitch of a sound is determined by the frequency of the sound wave. When a sound wave with a higher frequency reaches our ears, it is perceived as a higher-pitched sound. Similarly, a sound wave with a lower frequency is perceived as a lower-pitched sound.
- For example, when you pluck a guitar string tightly, it vibrates at a higher frequency, producing a higher-pitched sound. Conversely, when you pluck a guitar string loosely, it vibrates at a lower frequency, resulting in a lower-pitched sound.

Other factors:
While frequency is the primary factor that determines the pitch of sound, there are other factors that can influence our perception of pitch, such as:

Wavelength: The wavelength of a sound wave is inversely proportional to its frequency. Higher frequency sound waves have shorter wavelengths, while lower frequency sound waves have longer wavelengths. However, wavelength alone does not determine pitch.

Amplitude: The amplitude of a sound wave refers to its intensity or loudness. While amplitude does not directly affect pitch, it can influence our perception of pitch. A sound wave with a higher amplitude may be perceived as having a higher pitch, even if its frequency remains the same.

Time-period: The time period of a sound wave is the reciprocal of its frequency. It represents the time taken for one complete cycle of the wave. While time period is related to frequency, it is not a direct determinant of pitch.

Conclusion:
In conclusion, the pitch of sound is determined primarily by the frequency of the sound wave. The frequency represents the number of complete vibrations or cycles that occur in a given unit of time. Higher frequency sound waves are perceived as higher-pitched sounds, while lower frequency sound waves are perceived as lower-pitched sounds. While other factors such as wavelength, amplitude, and time period can influence our perception of pitch, frequency remains the primary determinant.

The number of vibration per second is called frequency. The pitch of sound depends upon frequency of sound.