High Pass Filter:
A high pass filter is an electronic circuit that allows high-frequency signals to pass through while attenuating low-frequency signals. It is commonly used in audio systems and communication devices to separate high-frequency components from the input signal.

Low Cut-Off Frequency:
The low cut-off frequency (also known as the corner frequency or -3dB frequency) is the point at which the output signal of a high pass filter starts to attenuate the input signal. Frequencies below the low cut-off frequency are greatly reduced or blocked in the output signal.

Pass Band Frequency:
The pass band frequency is the range of frequencies that are allowed to pass through a filter without significant attenuation. In a high pass filter, frequencies higher than the low cut-off frequency are considered to be in the pass band.

Explanation:
In a first-order high pass filter, frequencies higher than the low cut-off frequency are allowed to pass through with minimal attenuation. This means that these frequencies are part of the pass band.

The purpose of a high pass filter is to filter out low-frequency signals and allow high-frequency signals to pass through. The low cut-off frequency determines the point at which the filter starts attenuating the input signal. Frequencies below this cut-off point are greatly reduced or blocked in the output signal.

Therefore, frequencies higher than the low cut-off frequency are considered to be in the pass band of a high pass filter. These frequencies are not attenuated significantly and can be observed in the output signal.

Conclusion:
In a first-order high pass filter, frequencies higher than the low cut-off frequency are part of the pass band. This means that they are allowed to pass through with minimal attenuation. Frequencies below the low cut-off frequency are attenuated or blocked in the output signal.