A photoresistor cannot create an alternating current (AC) as it only changes resistance based on light levels and does not produce an alternating effect. While it can vary current levels, it does not generate negative current or respond quickly enough for high-frequency applications. Achieving an AC frequency in the range of light is not feasible with a photoresistor, and typical electrical devices like photodetectors respond to light amplitude rather than frequency. Suggestions for generating high-frequency AC include using a radio transmitter or appropriate electrical components like LEDs, but these do not produce actual AC currents at light frequencies. Overall, the discussion emphasizes the limitations of photoresistors in generating high-frequency AC and the challenges in achieving such frequencies with standard devices.