Question 2.(a) A beam of electrons is accelerated by a voltage of 180 V in a Davisson-Germer experi-ment. The electron beam is incident on the surface of a monocrystalline cobalt crystaloriented at 90° to the beam direction. A second-order beam is observed at 43.5°.What is the interatomic spacing of atoms in the cobalt crystal lattice?(b) The early experiments of Davisson & Germer used a polycrystalline nickel crystal. Ex-plain why they did not observe evidence for electron diffraction in their initial experi-ments.(c)i. A thermal neutron has an energy of E= 0.025 eV and a mass of 1.675 x 107 kg.Calculate the de Broglie wavelength of a thermal neutron.ii. On the basis of this result, explain whether it is possible to observe diffractioneffects when the neutron is scattered by a cobalt crystal. Suggest a reason whyperforming neutron diffraction experiments is challenging.

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(a) A beam of electrons is accelerated by a voltage of 180 V in a Davisson-Germer experi- ment. The electron beam is incident on the surface of a monocrystalline cobalt crystal oriented at 90° to the beam direction. A second-order beam is observed at 43.5°. What is the interatomic spacing of atoms in the cobalt crystal lattice?

(a) A beam of electrons is accelerated by a voltage of 180 V in a Davisson-Germer experi- ment. The electron beam is incident on the surface of a monocrystalline cobalt crystal oriented at 90° to the beam direction. A second-order beam is observed at 43.5°. What is the interatomic spacing of atoms in the cobalt crystal lattice?