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Questions and Answers
What was the primary objective of the electron diffraction experiment?
What was the primary objective of the electron diffraction experiment?
Who first suggested that matter might have wave-like properties?
Who first suggested that matter might have wave-like properties?
What was a significant outcome of Davisson and Germer's experiment?
What was a significant outcome of Davisson and Germer's experiment?
In the context of electron diffraction, what does the distance 'd' represent?
In the context of electron diffraction, what does the distance 'd' represent?
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What is the interference pattern in electron diffraction analogous to?
What is the interference pattern in electron diffraction analogous to?
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What discovery did Davisson and Germer make regarding electron behavior?
What discovery did Davisson and Germer make regarding electron behavior?
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What constant is used to determine the wavelength of matter according to de Broglie’s hypothesis?
What constant is used to determine the wavelength of matter according to de Broglie’s hypothesis?
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What effect did Clinton Davisson and Lester Germer discover in their experiment?
What effect did Clinton Davisson and Lester Germer discover in their experiment?
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What is the main purpose of the electron gun in this experiment?
What is the main purpose of the electron gun in this experiment?
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What feature of the carbon target causes the appearance of the interference pattern?
What feature of the carbon target causes the appearance of the interference pattern?
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How do you calculate the angle φ in the experiment?
How do you calculate the angle φ in the experiment?
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What is the minimum anode voltage required to see the rings?
What is the minimum anode voltage required to see the rings?
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What should be done after switching on the heater in the experiment?
What should be done after switching on the heater in the experiment?
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Which of the following describes the structure of the carbon used in the experiment?
Which of the following describes the structure of the carbon used in the experiment?
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What is the purpose of measuring the diffraction angle θ?
What is the purpose of measuring the diffraction angle θ?
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What happens to the rings as the accelerating voltage is adjusted?
What happens to the rings as the accelerating voltage is adjusted?
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What represents the de Broglie wavelength for an electron?
What represents the de Broglie wavelength for an electron?
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How is the momentum of electrons calculated as they leave the electron gun?
How is the momentum of electrons calculated as they leave the electron gun?
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What is the condition for constructive interference in wave diffraction?
What is the condition for constructive interference in wave diffraction?
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According to Bragg’s Law, what is the relationship between the wavelength, distance, and angle of diffraction?
According to Bragg’s Law, what is the relationship between the wavelength, distance, and angle of diffraction?
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What is the formula for calculating the intra-atomic distance in a crystal?
What is the formula for calculating the intra-atomic distance in a crystal?
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In the formula $d = rac{h}{2 ext{sin}( heta) ext{sqrt}(2emeVa)}$, what do the variables represent?
In the formula $d = rac{h}{2 ext{sin}( heta) ext{sqrt}(2emeVa)}$, what do the variables represent?
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Which of the following safety measures is essential when working with high voltage in the electron diffraction experiment?
Which of the following safety measures is essential when working with high voltage in the electron diffraction experiment?
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Which piece of equipment is NOT required for the electron diffraction experiment?
Which piece of equipment is NOT required for the electron diffraction experiment?
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What does the equation $L \sin 2\theta = R \sin \phi$ relate to in an experimental setup?
What does the equation $L \sin 2\theta = R \sin \phi$ relate to in an experimental setup?
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What is the significance of the distance L in the diffraction condition?
What is the significance of the distance L in the diffraction condition?
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Which equation involves the electron's velocity in relation to diffraction?
Which equation involves the electron's velocity in relation to diffraction?
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What is the main advantage of using electrons instead of light in microscopy?
What is the main advantage of using electrons instead of light in microscopy?
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What is the accepted value for the distance between the outer atomic layers in graphite?
What is the accepted value for the distance between the outer atomic layers in graphite?
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In what context is a scanning electron microscope (SEM) similar to an optical microscope?
In what context is a scanning electron microscope (SEM) similar to an optical microscope?
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In the study of diffraction, how should $1/V_a$ be plotted in relation to $sin \theta$?
In the study of diffraction, how should $1/V_a$ be plotted in relation to $sin \theta$?
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Which measurement needs to be compared against accepted values to validate distances in the experiment?
Which measurement needs to be compared against accepted values to validate distances in the experiment?
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Study Notes
Electron Diffraction Experiment
- Objective: Observe diffraction of electrons on a graphite target and calculate interatomic spacing in graphite.
Theoretical Background
- Wave-particle duality: Matter exhibits wave-like properties, as proposed by Louis de Broglie.
- De Broglie wavelength: λ = h/p, where h is Planck's constant and p is momentum.
- Electron diffraction: Electrons diffract from crystal planes, similar to light diffraction from a grating.
- Bragg's Law: nλ = 2d sin θ, where n is an integer, λ is electron wavelength, d is interatomic spacing, and θ is diffraction angle.
- Interatomic spacing calculation: d = λ / (2 sin θ).
Experimental Setup and Procedure
- Electron gun: Heats a cathode to emit electrons and accelerates them with an anode voltage (Va).
- Graphite target: Electrons diffract from the graphitized carbon target.
- Diffraction pattern: Circular rings on a phosphorus screen indicate constructive interference.
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Measurement procedure:
- Measure diffraction angle θ with masking tape and a ruler.
- Determine the arc length (s) of the diffraction rings.
- Calculate θ using formula: L sin 2θ = R sin φ, where L is target-screen distance, R is screen curvature radius, and φ is the angle between incident beam and diffracted beam.
Data Analysis
- Plot 1/Va versus sin θ for inner and outer rings.
- Calculate slope for each line.
- Determine interatomic spacing d10 (inner ring) and d11 (outer ring) from the slope.
Results
- Expected values for d10 and d11: 0.213 nm and 0.123 nm, respectively.
Applications
- Electron diffraction is a powerful tool for studying materials at atomic scale.
Limitations of Optical Microscopy
- Diffraction limit: Resolution limited by the wavelength of light (≈ 400 nm).
Scanning Electron Microscope (SEM)
- Uses electrons as "light" source to overcome the diffraction limit and achieve higher resolution.
- Magnetic lenses instead of glass lenses.
- Achieves angstrom-scale resolution allowing observations of very small features.
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Description
This quiz explores the fundamentals of electron diffraction, focusing on the theoretical background including wave-particle duality and Bragg's Law. You will learn how to calculate interatomic spacing in graphite using experimental observations. Test your knowledge on electron behavior and experimental processes related to diffraction.
