Matter Waves: Electrons Emerge from an Electron Gun with a Speed

question 20

Multiple Choice

Matter waves: Electrons emerge from an electron gun with a speed of 2.0 × 10⁶ m/s and then pass through a pair of thin parallel slits. Interference fringes with a spacing of 2.7 mm are detected on a screen far from the double slit and fairly close to the center of the pattern. What would the fringe spacing be if the electrons were replaced by neutrons with the same speed? (m_el = 9.11 × 10^-31 kg, m_neutron = 1.67 × 10^-27 kg)

• A) 1.5 µm
• B) 4.9 µm
• C) 0.93 nm
• D) 1.1 µm
• E) 1.5 nm

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