Photons/Second from a 100W bulb.

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In summary, the number of photons emitted per second from a 100W bulb can vary, but on average it is around 1.2 x 10^20. The wattage of a bulb directly affects the number of photons emitted per second - a higher wattage results in more photons being emitted. While the formula E=hf can be used to calculate the number of photons emitted per second for individual photons, it cannot be used for the total number emitted from a bulb. The color of light does not directly affect the number of photons, but different frequencies can affect the energy of individual photons. The number of photons emitted per second is not constant and can be affected by factors such as bulb condition, temperature, humidity, and altitude.
  • #1
Brammo
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Homework Statement



Estimate how many photons of visible light (500 nm) are emitted by a 100 W Bulb.

The answer on the sheet says approximately 10[itex]^{20}[/itex] photons/second

However when I work it out I get a slightly different answer.

Homework Equations



I used that 1J=1W/s or E=P/t

Also Energy of one photon is E=hf so if you had lots of photons you would [itex]\Delta[/itex]E=nhf where n is the number of photons.

The Attempt at a Solution



I get 2.5[itex]\times[/itex]10[itex]^{20}[/itex] photons/second
 
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  • #2
You solved the problem correctly.
 

1. How many photons are emitted per second from a 100W bulb?

The number of photons emitted per second from a 100W bulb depends on various factors such as the type of bulb, its efficiency, and the wavelength of light being emitted. However, on average, a 100W bulb can emit around 1.2 x 10^20 photons per second.

2. How does the wattage of a bulb affect the number of photons emitted per second?

The wattage of a bulb is directly proportional to the number of photons emitted per second. This means that as the wattage of a bulb increases, the number of photons emitted per second also increases. Therefore, a 100W bulb will emit more photons per second compared to a 50W bulb.

3. Can the number of photons emitted per second be calculated using the formula E=hf?

Yes, the number of photons emitted per second can be calculated using the formula E=hf, where E is the energy of a single photon, h is Planck's constant, and f is the frequency of light. However, this formula only applies to individual photons and cannot be used to calculate the total number of photons emitted per second from a bulb.

4. How does the color of light emitted affect the number of photons per second?

The color of light emitted does not directly affect the number of photons per second. However, different colors of light have different frequencies, which can affect the energy of individual photons. This means that a red light bulb and a blue light bulb of the same wattage may emit a different number of photons per second.

5. Is the number of photons emitted per second from a bulb constant?

No, the number of photons emitted per second from a bulb is not constant. It can vary depending on the condition of the bulb, the temperature, and the surrounding environment. For example, a bulb may emit more photons per second when it is first turned on, and the number may decrease as the bulb heats up. Additionally, factors such as humidity and altitude can also affect the number of photons emitted per second.

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