Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis. Explain how high-speed electrons are produced in the apparatus in Figure 1. In your answer you should: • name parts A and B • discuss the purposes of potential differences $V_1$ and $V_2$. [4 marks] In the experiment, electrons are incident on a target made of a crystalline material. The electron wavelengths need to be about 50% the size of an atom to produce a diffraction pattern on the screen. Suggest a suitable value for $V_2$. $V_2 = $ ____ V [4 marks] Figure 2 shows a typical diffraction pattern produced on the screen by the electrons. Explain how measurements made with the apparatus in Figure 1 can be used to support the de Broglie hypothesis. [4 marks] STM and TEM are abbreviations for two types of electron microscope. Which row links the type of microscope to a relevant property of moving electrons? Tick (✓) one box.

A-Level AQA Physics The Photoelectric Effect: Figure 1 shows the apparatus use

Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis - AQA - A-Level Physics - Question 1 - 2021 - Paper 7

Question 1

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Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis. Explain how high-speed electrons are produced ... show full transcript

Worked Solution & Example Answer:Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis - AQA - A-Level Physics - Question 1 - 2021 - Paper 7

Step 1

Explain how high-speed electrons are produced in the apparatus in Figure 1.

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Answer

Part A is the heated cathode, which emits electrons due to thermionic emission when heated. Part B is the anode, which is positively charged to attract the emitted electrons. The potential difference $V_1$ provides the energy to heat the cathode, ensuring a sufficient current of electrons is emitted. The potential difference $V_2$ accelerates the emitted electrons towards the target.

Step 2

Suggest a suitable value for $V_2$.

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Answer

Given that the atom diameter is approximately 0.1 nm (or $1 imes 10^{-10}$ m), the corresponding wavelength for electron diffraction can be calculated using the de Broglie equation: $ext{wavelength} = rac{h}{p} = rac{h}{mv}$ Assuming a suitable momentum relationship, a suitable potential difference $V_2$ can be found using the formula: $ext{KE} = eV_2$ This will yield a value for electrons with the required wavelength, which should be around $0.05 ext{ V}$ . The exact value may vary based on additional parameters.

Step 3

Explain how measurements made with the apparatus in Figure 1 can be used to support the de Broglie hypothesis.

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Answer

The de Broglie hypothesis posits that particles, such as electrons, exhibit wave-like properties. By measuring the diffraction pattern produced when electrons pass through a crystalline target, we can observe the wave properties of electrons. The wavelength derived from electron energy can be compared to the observed diffraction patterns, providing experimental support for the wave-particle duality concept. These measurements illustrate the predicted relationships between wavelength and momentum, reinforcing de Broglie's theory.

Step 4

Which row links the type of microscope to a relevant property of moving electrons? Tick (✓) one box.

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Answer

For STM: Moving electrons can cross a potential barrier. For TEM: Moving electrons can be deflected by a magnetic field.

Note: Tick the appropriate box linking each type of microscope to the indicated properties.

Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis - AQA - A-Level Physics - Question 1 - 2021 - Paper 7

Worked Solution & Example Answer:Figure 1 shows the apparatus used in an experiment to investigate electron diffraction and the de Broglie hypothesis - AQA - A-Level Physics - Question 1 - 2021 - Paper 7

Explain how high-speed electrons are produced in the apparatus in Figure 1.

Suggest a suitable value for $V_2$.

Explain how measurements made with the apparatus in Figure 1 can be used to support the de Broglie hypothesis.

Which row links the type of microscope to a relevant property of moving electrons? Tick (✓) one box.

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