How Many Photons Does a 25W Monochromatic Light Bulb Emit Per Second?

In summary, the photoelectric effect is a phenomenon where light causes electrons to be emitted from a material surface. It was first observed by Heinrich Hertz in 1887 and explained by Albert Einstein in 1905. It provided evidence for the particle nature of light and led to the development of photovoltaic cells. The effect is affected by factors such as the frequency and intensity of light, and is used in technologies such as solar panels, photomultiplier tubes, and photoelectric sensors. It is also used in photoelectric spectroscopy for analytical purposes.
  • #1
soul5
64
0
How many photons per second are emitted by a monochromatic light bulb (650nm) that emits 25 W of power?

W=hfo

hf=Ek + W

P=W/t


is there a way we can find power? how do I solve this question?
 
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  • #2
Hint: What's the energy of a single 650nm photon? (This is not a photoelectric effect problem.)
 
  • #3


To solve this question, we can use the equation P = hfN, where P is power, h is Planck's constant, f is the frequency of the light, and N is the number of photons per second. We can rearrange this equation to solve for N, which will give us the number of photons per second emitted by the light bulb.

First, we need to find the frequency of the light. We know that the wavelength is 650nm, so we can use the equation c = fλ, where c is the speed of light (3.00 x 10^8 m/s). Rearranging this equation, we get f = c/λ. Plugging in the values, we get f = (3.00 x 10^8 m/s) / (650 x 10^-9 m) = 4.62 x 10^14 Hz.

Next, we can plug this frequency value into the equation P = hfN and solve for N. We also need to convert the power from watts to joules/second, so we multiply 25 W by 1 J/s. This gives us:

25 J/s = (6.626 x 10^-34 J*s)(4.62 x 10^14 Hz)N

Solving for N, we get N = 3.23 x 10^19 photons/second.

Therefore, a monochromatic light bulb emitting 25 W of power at a wavelength of 650nm would emit approximately 3.23 x 10^19 photons per second.
 

FAQ: How Many Photons Does a 25W Monochromatic Light Bulb Emit Per Second?

What is the photoelectric effect?

The photoelectric effect is a phenomenon where light, typically in the form of photons, strikes a material surface and causes electrons to be emitted from the surface. This process is also known as photoemission.

Who discovered the photoelectric effect?

The photoelectric effect was first observed by physicist Heinrich Hertz in 1887. In 1905, Albert Einstein provided a theoretical explanation for the phenomenon, for which he received the Nobel Prize in Physics in 1921.

What is the significance of the photoelectric effect?

The photoelectric effect is significant because it provided evidence for the particle nature of light and the concept of energy quantization. It also led to the development of photovoltaic cells, which are used in solar panels to convert light energy into electricity.

What factors affect the photoelectric effect?

The photoelectric effect is affected by the frequency and intensity of the incident light, as well as the properties of the material surface, such as its work function and the number of available electrons. The photoelectric effect also follows the laws of conservation of energy and momentum.

How is the photoelectric effect used in modern technology?

The photoelectric effect is used in various technologies, including photovoltaic cells for solar energy, photomultiplier tubes for detecting light, and photoelectric sensors for detecting motion or proximity. It is also used in photoelectric spectroscopy, which is a powerful analytical technique in chemistry and physics.

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