State what the de Broglie wavelength means.
Fig. 7.1 shows a glass tube in which electrons are accelerated by a high p.d. to make a beam directed at a thin graphite crystal. After passing through the graphite crystal, the electrons reach the fluorescent screen. The screen glows wherever the electrons strike it. Fig. 7.2 shows the fluorescent screen viewed end-on, from the right-hand side of Fig. 7.1.
State the name of the phenomenon shown by the pattern in Fig. 7.2.
Explain what can be concluded from the pattern in Fig. 7.2 about the nature of electrons.
The electrons in (b) are now accelerated across a larger potential difference between the cathode and the anode.
On Fig. 7.3, sketch the pattern now visible on the fluorescent screen in Fig. 7.1.
Explain, referring to de Broglie wavelength, how the pattern on the fluorescent screen changes.