Assertion : When current through a bulb decreases by $0.5\%$, the glow of bulb decreases by $1\%$.
Reason : Glow (Power) which is directly proportional to square of current.
AIIMS 2015, Medium
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Glow $=$ Power $(P) =I^2R$
$\therefore \,\frac{{dP}}{P} = 2\left( {\frac{{dI}}{I}} \right) = 2\, \times \,0.5\, = \,1\,\% $
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