Wave-particle duality and de Broglie wavelengthEdexcel A-Level Physics: Flashcards

What these 12 flashcards ask

What is wave-particle duality?
State the de Broglie equation.
What is the value of the Planck constant?
What evidence shows that electrons have wave properties?
What causes the rings in electron diffraction?
Why must the electron wavelength be comparable with the atomic spacing?
What happens to the rings if the accelerating potential difference is increased?
What is the kinetic energy of an electron accelerated from rest through potential difference V?
How does the wavelength change if momentum doubles?
Approximately how large is the de Broglie wavelength of an electron at 4.0 × 10⁶ m s⁻¹?
Why can we not observe diffraction of a cricket ball?
Which has the shorter wavelength at the same kinetic energy, a proton or an electron?

Exam questions on Wave-particle duality and de Broglie wavelength

Electrons travelling at a speed of 4.0 × 10⁶ m s⁻¹ are directed at a thin crystal in an evacuated tube. The spacing between neighbouring atoms in the crystal is about 2 × 10⁻¹⁰ m. The Planck constant is 6.63 × 10⁻³⁴ J s and the mass of an electron is 9.11 × 10⁻³¹ kg.
Explain why a beam of these electrons would be expected to show noticeable diffraction at the crystal.2 marks
In an electron diffraction tube, electrons are accelerated through a potential difference in a vacuum and directed at a thin film of graphite. They then strike a fluorescent screen, where a pattern of concentric bright rings is seen.
Explain how the ring pattern shows that electrons have wave properties.2 marks
Electrons are released from rest and accelerated through a potential difference of 250 V in a vacuum, then directed at a thin crystal. The electron charge is 1.60 × 10⁻¹⁹ C, the electron mass is 9.11 × 10⁻³¹ kg and the Planck constant is 6.63 × 10⁻³⁴ J s.
Calculate the speed of the electrons after acceleration.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).