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The brightness of an incandescent light ...

The brightness of an incandescent light bulb is con- trolled by a regulator. The regulator is a variable resistor connected in series with the bulb. What happens to the colour of the light given off by the bulb as the resistance of the regulator is increased? What happens to the average energy of photons given out by the bulb? Does it increase?

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The correct Answer is:
It become reddish. Average photon enrgy decreases.
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Knowledge Check

  • What happens when we switch on a light bulb?

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    The filament or wire inside it burns with a yellow flame.
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    The filament gets active and glows.
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    increase
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  • Three 100 W light bulbs are connected in series to a 220V power source. If two of the light bulbs are replaced by 60 W bulbs, the brightness of the remaining on w bulb is

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