After a long period of use, a grey spot develops inside of a bulb. This is because

A Dust inside the bulb condenses on the top

B Glass undergoes a change due to the heat

C The heat of the bulb scorches the glass at the top

D The tungsten filament evaporates and collects there

Answer & Explanation
Answer: Option [A]

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Physics - General Science Objective Questions and Answers for Competitive Exams