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Re: [Phys-l] Hewitt's three answers



Interesting; thanks for sharing. Your observations show that I was wrong, thinking that variations of intensity would not be noticeable.

Ludwik
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On Mar 28, 2012, at 6:22 PM, Tom Bross wrote:

I recently took a slow motion video of a drop forming and falling from a spigot at 410 frames per second. I illuminated the area with a 100 W incandescent light bulb and on playback I noticed the variation in brightness of the white wall in the background, no doubt due to the small but noticeable cooling and warming of the bulb's filament.

Sent from my iPhone

On Mar 28, 2012, at 4:44 PM, Ludwik Kowalski <kowalskil@mail.montclair.edu> wrote:

Look at Hewitt's "Flash Frequency" question (page 202 in the April 2012, issue ofThe Physics Teacher). In my opinion all three answers, in this multiple choice test are incorrect, in my opinion. My answer would be 0 flashes.

Yes, there are 120 current maxima in each second. But the light intensity, in the case of an incandescent light bulb, is practically constant due to "thermal inertia." Do you agree?


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Forum for Physics Educators
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