(a)[2]
State the equation for the de Broglie wavelength $\lambda$ of a particle in motion. State the meaning of any other symbol used.
(b(i))[1]
State the name of the phenomenon shown by the electrons at the crystal.
(b(ii))[1]
State what this phenomenon shows about the nature of electrons.
(b(iii))[1]
Suggest why the thin crystal leads to the phenomenon in (b)(i).
(b)
Electrons are accelerated through a potential difference, then pass through a thin crystal and finally strike a fluorescent screen. The pattern in Fig. 8.1 is seen on the fluorescent screen.
(b(iv))[2]
The electron is accelerated through a different potential difference. Fig. 8.2 shows the pattern now seen on the screen. State and explain how the potential difference was changed to produce the pattern shown in Fig. 8.2.