Correct option is D
The outer tube of a high-pressure metal halide lamp is made of borosilicate glass primarily to reduce the ultraviolet radiation from the lamp. So the answer is (d).
Explanation: Borosilicate glass has the property of filtering out a significant portion of the UV radiation produced by the inner arc tube of the metal halide lamp, protecting users from potential harm.
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UV protection:
The main reason for using borosilicate glass is its ability to block UV radiation.
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Heat resistance:
Borosilicate glass also has good thermal resistance, which is important considering the high temperatures generated by the lamp.
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Protection of inner tube:
The outer glass envelope protects the inner quartz arc tube from physical damage.
