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According to the table of energy magnitudes, a single electron in an old television tube's beam carries about 4.0 x 10^-15 joules, while the energy needed to break one DNA strand is about 10^-19 joules. About how many DNA strands could that much energy break, if fully transferred?
AAbout 4 strands broken
BAbout 400 strands broken
CAbout 40,000 strands broken
DAbout 4,000,000 strands
Answer & Solution
Correct answer: C. About 40,000 strands broken
1. The number of DNA strands breakable is the electron's energy divided by the energy needed per strand.
2. Dividing 4.0 x 10^-15 J by 10^-19 J means subtracting the exponents, negative 15 minus negative 19, which leaves positive 4.
3. That gives 4.0 times 10 to the 4th power, which is 40,000.
4. 4 and 400 strands are each too small by several orders of magnitude, and 4,000,000 strands overshoots the correctly computed exponent by two additional powers of ten.
_Source: OpenStax College Physics (CC BY 4.0), Ch 7 "Work, Energy, and Energy Resources", section 7.6 Conservation of Energy_
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