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Question
The "after glow" from some clock faces is caused by atoms1) being excited,
2) vibrating at frequencies greater than a million billion times per second,
3) remaining for some time in a state of excitation before de-exciting,
and materials exhibiting this property are called
4) fluorescent.
5) phosphorescent.
6) incandescent.
7) luminescent.
Answer
This answer is hidden. It contains 3 characters.
Related questions
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