F287- Efek fotolistrik fisika kuantum : Teori plus contoh soal

Summary

This video script explores the physics behind the photoelectric effect, explaining key concepts such as the relationship between light frequency and the kinetic energy of ejected electrons. It covers the calculation of stopping potential and energy in electron volts, with practical examples to demonstrate how to use Planck’s constant and energy-frequency equations. The script delves into the effects of different light frequencies on the ejected electron's energy, using graphs and conversions between joules and electron volts to determine the necessary frequency for the photoelectric effect to occur.

Takeaways

• 😀 The photoelectric effect is discussed, emphasizing how light causes electrons to be ejected from a metal surface.
• 😀 The formula relating kinetic energy (Eₖ) to frequency (f) and the work function (Φ) is introduced: Eₖ = hf - Φ.
• 😀 The maximum kinetic energy of an electron is found by calculating the potential stopping voltage (V), with V = 0.2 V.
• 😀 The energy of the ejected electron is given in electron volts (eV), and the relationship between kinetic energy and stopping potential is explored.
• 😀 The energy kinetic calculation uses the electron charge value (1.6 × 10⁻¹⁹ C) and the corresponding potential energy formula.
• 😀 The Planck constant (h = 6.63 × 10⁻³⁴ J·s) and frequency (f) are crucial in solving for kinetic energy in photoelectric problems.
• 😀 Conversion between electron volts (eV) and joules (J) is necessary for consistent units in the calculations.
• 😀 The frequency required to release electrons is calculated using the equation, with units carefully adjusted to match the values on both sides of the equation.
• 😀 The graph helps visualize the relationship between the maximum kinetic energy and the frequency of light, where the intercept with the energy axis is used to find the work function.
• 😀 The result of the calculations shows the frequency of light needed to achieve a specific kinetic energy of 1.2 eV is approximately 0.8 × 10¹⁵ Hz.

Q & A

What is the photoelectric effect and how does it relate to the energy of electrons?

The photoelectric effect refers to the phenomenon where electrons are ejected from a metal surface when it is exposed to light. The energy of the ejected electrons depends on the frequency of the incoming light. The maximum kinetic energy of the electrons is determined by the formula E = hf - W₀, where E is the kinetic energy, h is Planck's constant, f is the frequency of the light, and W₀ is the work function of the metal.

What is the significance of the stopping potential in the photoelectric effect?

The stopping potential is the voltage required to stop the ejected electrons from reaching the anode. It corresponds to the maximum kinetic energy of the electrons, and it is directly related to the energy of the incident photons. The stopping potential is used to measure the maximum kinetic energy of the emitted electrons.

How is the stopping potential related to the kinetic energy of the ejected electrons?

The stopping potential is proportional to the maximum kinetic energy of the ejected electrons. The kinetic energy of the electrons can be measured in electron volts, and the stopping potential, in volts, is numerically equal to the kinetic energy when expressed in electron volts.

What is Planck's constant, and how is it used in these calculations?

Planck's constant (h) is a fundamental physical constant used to describe the relationship between the energy of a photon and its frequency. In the photoelectric effect, it is used in the formula E = hf - W₀, where E is the energy of the ejected electron, f is the frequency of the incident light, and W₀ is the work function of the material.

How do we convert from electron volts to Joules in the context of the photoelectric effect?

To convert from electron volts (eV) to Joules (J), we multiply the energy in eV by the charge of an electron (1 eV = 1.6 × 10⁻¹⁹ J). This is important when using different units in calculations involving the photoelectric effect, as energy can be expressed in either electron volts or Joules.

What does the frequency of the light impact in the context of the photoelectric effect?

The frequency of the light affects the kinetic energy of the ejected electrons. If the frequency is above a certain threshold, the electrons will be ejected with a kinetic energy proportional to the frequency of the light. If the frequency is below the threshold, no electrons will be ejected, regardless of the intensity of the light.

Why is the work function (W₀) important in the photoelectric effect?

The work function (W₀) is the minimum energy required to release an electron from the metal's surface. It represents the threshold energy that the incoming photons must overcome in order for electrons to be ejected. The kinetic energy of the emitted electrons is the difference between the photon energy (hf) and the work function (W₀).

How does the energy of the incident photons relate to the kinetic energy of the emitted electrons?

The energy of the incident photons is absorbed by the electrons. If the photon energy is greater than the work function, the excess energy becomes the kinetic energy of the emitted electrons. The relationship is given by E = hf - W₀, where E is the kinetic energy, h is Planck's constant, f is the photon frequency, and W₀ is the work function.

How can we calculate the frequency of light required to achieve a certain energy in the photoelectric effect?

The frequency required to achieve a certain kinetic energy for the ejected electron can be calculated using the formula E = hf - W₀. Rearranging this equation to solve for frequency, we get f = (E + W₀) / h. The frequency can be adjusted to match the desired kinetic energy of the electrons.

What can be concluded about the relationship between photon frequency and electron kinetic energy?

The kinetic energy of the emitted electrons increases with the frequency of the incident photons, as long as the frequency is above the threshold required to overcome the work function. This relationship demonstrates that the photoelectric effect is frequency-dependent, not intensity-dependent, as increasing light intensity (while keeping frequency constant) does not increase the energy of the emitted electrons.