Introduction:
Mica capacitors are widely used at very high frequencies due to their low ohmic losses and less reactance. This makes them suitable for applications where high-frequency performance is crucial. In this response, we will explore the reasons why mica capacitors are preferred at high frequencies.

Low Ohmic Losses:
- Mica capacitors exhibit low ohmic losses, which means they dissipate less energy in the form of heat.
- This is advantageous at high frequencies because any energy loss in the capacitor would result in reduced efficiency and increased heating.
- The low ohmic losses of mica capacitors ensure that the energy loss is minimized, making them ideal for high-frequency applications.

Less Reactance:
- Reactance is the opposition offered by a capacitor to the flow of alternating current.
- At high frequencies, the reactance of a capacitor becomes more significant.
- Mica capacitors have a relatively low reactance compared to other capacitor types, such as ceramic or electrolytic capacitors.
- This low reactance allows mica capacitors to effectively store and release energy at high frequencies without significantly impeding the alternating current flow.

Additional Energy for Reversal of Dielectric:
- In an AC field, the dielectric of a capacitor needs to reverse its polarization with each alternating cycle.
- The energy required for this reversal is relatively small in mica capacitors.
- This is due to the properties of mica, which has a high dielectric strength and low dielectric losses.
- As a result, mica capacitors can efficiently handle the energy requirements for the reversal of the dielectric, making them suitable for high-frequency applications.

Retention of Charge:
- Mica capacitors have low leakage currents, which means that they do not lose their stored charge easily.
- This is beneficial in high-frequency applications where the capacitor needs to retain its charge for longer periods.
- The negligible retention of charge in mica capacitors ensures that the stored energy is available when needed, without significant loss over time.

Conclusion:
In summary, mica capacitors are preferred at very high frequencies due to their low ohmic losses, less reactance, small additional energy required for reversal of the dielectric, and negligible retention of charge. These characteristics make mica capacitors suitable for high-frequency applications where efficient energy storage and release are essential.