Even if the switch ‘instantly’ completed the circuit, electricity does not move along a wire at the ‘speed of light’, but only about 66% of that speed. If the light contains a filament, it has to heat up to several hundres of degrees before it’s visible. Fluorescent takes longer; even an LED does not shed light ‘instantly’. So he was wrong on multiple counts. BUT they don’t teach such details in college (except in physics classes). AFAIK,most junior high ‘science’ teachers are not all that familiar with such details.
Even if the switch ‘instantly’ completed the circuit, electricity does not move along a wire at the ‘speed of light’, but only about 66% of that speed. If the light contains a filament, it has to heat up to several hundres of degrees before it’s visible. Fluorescent takes longer; even an LED does not shed light ‘instantly’. So he was wrong on multiple counts. BUT they don’t teach such details in college (except in physics classes). AFAIK,most junior high ‘science’ teachers are not all that familiar with such details.