<prompt> Single wavelength light is emitted by:QTHLEDArgon laserPAC  <response>: Argon laser light has wavelength of 470 nm which is monochromatic single wavelength or frequency in nature. It produces an intensity of 200 to 300 mW.Ref: Textbook of Operative Dentistry, Nisha and Amit Garg, 3rd edition, Pg no:277 