The frequency is 365 nm.

By stark contrast, the higher quality, more expensive torches producing the 365nm wavelength, produce a near pure UV output which is the optimum frequency for UV fluorescence.

This means, you will see far more detail and in a greater range of colours than any other wavelength.  As these units generate less unwanted Interference light, they may naturally appear weaker or darker. This can be misleading and should not be misinterpreted. 

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