He them put chloride in each color to see the outcome. The red caused a small change while the deep violet darkened the chloride. Ritter placed chloride in the lightless area just beyond the violet and it darkened as it were in a smoky fire. The was evidence of another wave form just barely higher than the violet of visible light. It is now known as ultraviolet or UV light.
Blisters can occur due to too much exposure.
Ultraviolet waves are effective in killing bacteria and viruses. Hospitals use germicidal lamps that produce these waves to sterilize equipment, water and air in operating rooms. It is also used to treat acne and psoriasis. The Food and Drug industry uses germicidal lamps to disinfect various types of products and their containers. The main use of ultraviolet is in the manufacturing integrated circuits.