This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Single wavelength light is emitted by: 
Select and explain. 
A. QTH, B. LED, C. Argon laser, D. PAC
C: Argon laser
Answer: C: Argon laser 
Explanation: 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