Quick questions on Wave-particle duality and de Broglie: WACE Year 12 Physics Unit 4

Louis de Broglie reasoned that if waves can act as particles, particles might act as waves. He assigned every moving particle a wavelength

When a beam of electrons is fired at a thin crystal or graphite film, it produces concentric diffraction rings on a screen, exactly the pattern expected when waves pass through a regular array of slits. Particles alone could not interfere to form rings, so this confirms that matter has a wave nature, validating de Broglie's idea.

Use $\lambda=h/mv$ with momentum in kg m s-1, and remember that a larger momentum gives a shorter wavelength. If a voltage is given instead of a speed, first find the speed from $qV=\tfrac{1}{2}mv^2$, then the momentum.