Summary:
A 395nm LED emits more visible light than a 365nm UV LED. The 395nm UV light produces a noticeable purple glow, while the 365nm UV light emits a faint bluish-white glow, caused by residual energy “spilling” into the visible spectrum. Both wavelengths fall within the UV-A range and are commonly used for blacklight effects or curing applications.
Differences Between 365nm and 395nm UV Lights
Both 365nm and 395nm options fall within the UV-A wavelength range. In general, UV-A lights are used for creating and observing fluorescent effects, as well as for curing plastics and paints. Compared to the stronger UV-B and UV-C rays, UV-A is much safer.
So, what does the 30nm difference mean?
The main distinction is that a 395nm LED emits more visible light. A 395nm UV LED gives off a clear purple glow, while a 365nm UV LED produces a dim bluish-white glow due to residual energy trailing into the visible spectrum. Both, however, emit in the UV-A range and are capable of producing blacklight or curing effects.
Why Is There a Difference in Visible Light?
A spectrum output chart of 365nm (narrow dotted line) and 395nm (wide dotted line) LEDs shows that both emit light not only at their peak wavelength but also above and below it. In other words, a 395nm LED doesn’t emit strictly at 395nm.
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395nm LEDs peak at 395nm but also release significant energy at 400nm and even 410nm, which fall within the visible violet range. That’s why they appear visibly purple. They still emit some UV-A wavelengths below 395nm, which remain effective for fluorescence and UV-A reactions, but the majority of energy is in the visible violet area.
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365nm LEDs emit nearly all their energy in the invisible UV-A range, with output decreasing steadily before reaching 400nm. This maximizes usable UV-A energy and minimizes visible light, making them preferable for most UV applications.
When you turn on a 365nm LED, you may still notice a faint bluish-white glow. This comes from minimal visible light “leakage,” where a small amount of visible spectrum energy (white light) is also emitted. While this is too small to register on most spectrum charts, it can still be noticeable in certain applications—such as UV photography—where it may be disruptive. In such cases, additional visible light filtering may be necessary.
Fluorescence: 365nm vs. 395nm
Beyond avoiding visible purple glow, 365nm UV lights have another advantage: stronger fluorescence. Many objects fluoresce most strongly at 365nm, as proven by absorption spectrum measurements.
As a result, 365nm UV lights are often the better choice for applications that require stronger fluorescence effects. Combined with their minimal visible purple light output, they are considered the superior option when performance is critical.