Which feature glows orange under ultraviolet light on the $10 bill?

• A. Watermark
• B. Color shifting ink
• C. Microprinting
• D. Security thread

Answer: (D)

Under ultraviolet light, features that fluoresce are used for quick authenticity checks. The security thread on the ten-dollar bill is designed to glow with UV exposure because it contains fluorescent material embedded in the note. This vertical thread emits orange light, making it easy to verify a genuine bill at a glance, which is why it’s the feature that glows orange under UV light. Other features work differently: a watermark appears when held up to light, not as a UV glow; microprinting is tiny text that’s best seen with magnification; and color-shifting ink changes hue with viewing angle, not with UV illumination. Understanding this helps you spot a genuine bill quickly by looking for the orange glow from the security thread.