This versatile precision ultraviolet (UV) lamp combines two functions in one device: stamps, banknotes, credit cards, telephone cards, etc. can be examined for both fluorescence and phosphorescence. The combination of short and long UV rays (switchable between 254 and 380 nm) makes this lamp especially practical for the user. Long wave UV lamps help the currency and stamp collector to identify fluorescent paper and inks. They are an important tool to verify authenticity and to check for repairs or forgeries. Long wave ultraviolet light typically has a wavelength of approximately 366nm (nanometers). Short wave ultraviolet light with a wavelength of approximately 254 nm is used to identify phosphorescence. 4 Watt (254 nm) or 3-4 mW (380 nm). Requires four AA batteries (not included).