Photoelectric Effect, Threshold Frequency etc.

In summary, the given scenario involves light of intensity 1.5 x 10^-2 Wm/2 and wavelength 250 x 10^-9m incident on an iron surface with an area of 1 x 10^-4 m^2. The surface reflects 95% of the light and the threshold frequency for iron is 1.1 x 10^15 Hz. The questions to be answered are: 1) the intensity of light available for the photoelectric effect, 2) the number of electrons emitted per second, 3) the work function in electron volts for iron, and 4) the stopping potential for this radiation. It is important to note that (x) in this instance represents to
  • #1
Andresx90
8
0

Homework Statement


Light of intensity 1.5 x 10 (x)-2 Wm/2 and wavelength 250 x 10 (x)-9m is incident on an iron surface of area 1 x 10 (x) -4 m2. The iron surface reflects 95% of the light. The threshold frequency for iron is 1.1 x 10x15 Hz.
Calculate:
1) The intensity of light available for the photoelectric effect
2) The number of electrons emitted per second
3) The work function in electron volts for iron
4) The stopping potential for this radiation

Could someone answer this question for me showing working used as well.

(x) in this instance means to the power of.



Homework Equations





The Attempt at a Solution



1) 95% of the light intensity already given (no calculator)
 
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  • #2
We will not answer the questions for you here at PF. We can help guide you to the answer but most of the work has to be your own. Please refer to the forum guidelines.

https://www.physicsforums.com/showthread.php?t=5374

Please post your attempt at the other parts of the question.
 
  • #3


= 1.42 x 10^-2 W/m^2

2) To calculate the number of electrons emitted per second, we can use the photoelectric effect equation:

Kmax = hf - φ

Where Kmax is the maximum kinetic energy of the emitted electron, hf is the energy of the incident photon, and φ is the work function of the material. In this case, we are given the threshold frequency, so we can rearrange the equation to solve for the number of electrons emitted per second:

n = (I/A)(1 - R)/hf

Where n is the number of electrons emitted per second, I is the intensity of light, A is the area of the surface, R is the reflectivity (given as 95%), and hf is the energy of the incident photon. Plugging in the values given, we get:

n = (1.42 x 10^-2 W/m^2)(1 - 0.95)/(6.63 x 10^-34 J·s)(2.50 x 10^-7 m^2)

= 1.48 x 10^17 electrons/s

3) To find the work function in electron volts, we can use the relation:

1 eV = 1.602 x 10^-19 J

So, the work function in electron volts is:

φ = (1.1 x 10^15 Hz)(6.63 x 10^-34 J·s) = 7.28 x 10^-19 J

= 7.28 x 10^-19 J/1.602 x 10^-19 J/eV = 4.54 eV

4) The stopping potential is the minimum potential needed to stop the flow of electrons emitted from the surface. We can use the equation:

Vstop = Kmax/e

Where Vstop is the stopping potential, Kmax is the maximum kinetic energy of the emitted electron, and e is the elementary charge. Plugging in the values calculated in parts 1 and 2, we get:

Vstop = (1.42 x 10^-2 W/m^2)(1 - 0.95)/(1.48 x 10^17 electrons/s)(1.602 x 10^-19 C)

= 1.52 x 10^-19 V

Therefore, the stopping potential for this radiation is 1.52 x 10^-19 V.
 

1. What is the Photoelectric Effect?

The Photoelectric Effect is a phenomenon in which electrons are emitted from a material when it is exposed to electromagnetic radiation, such as light. This effect was first observed by Heinrich Hertz in 1887 and later explained by Albert Einstein in 1905 through his theory of the quantized nature of light.

2. What is the Threshold Frequency?

The Threshold Frequency is the minimum frequency of electromagnetic radiation required to cause the emission of electrons from a material in the Photoelectric Effect. Below this frequency, no electrons will be emitted regardless of the intensity of the light. The threshold frequency depends on the type of material and can vary from one material to another.

3. How does the Photoelectric Effect support the wave-particle duality of light?

The Photoelectric Effect supports the wave-particle duality of light by demonstrating that light can behave as both a wave and a particle. The emission of electrons from a material is a particle-like behavior, while the varying intensity of the emitted electrons depending on the frequency of light is a wave-like behavior.

4. What is the work function?

The work function is the minimum amount of energy required to remove an electron from the surface of a material in the Photoelectric Effect. It is different for each material and is directly related to the threshold frequency. The higher the work function, the more difficult it is to remove electrons from the material.

5. How is the Photoelectric Effect used in everyday life?

The Photoelectric Effect has many practical applications in everyday life. Some examples include photovoltaic cells used in solar panels to convert sunlight into electricity, photoelectric sensors used in automatic doors and elevators, and photocells used to detect light and turn on streetlights. It is also used in various scientific instruments and experiments to study the properties of light and electrons.

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