This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2018, Subject name: Dental
Patients with porphyria are highly sensitive to which wavelength : 
Select and explain. 
A. 290-320 nm, B. 400-420 nm, C. 320-400 nm, D. 250-290 nm
B: 400-420 nm
Answer: B: 400-420 nm 
Explanation: Porphyrin are excited by visible light with a wavelength between 400 and 410 nm and emit an intense red fluorescence. The released energy reacts with oxygen to produce free radicals and singlet oxygen that damages tissues Mc porphyria - porphyria cutaneatarda (if- Red urine - D/D - myoglobinuria )