The de Broglie wavelength is an important idea in physics that shows that all matter with mass can also show wave-like properties. For example, an electron (which we usually think of as a particle) can diffract around a corner. Heavier objects like molecules can also do this in extreme circumstances. Even something as large as a tennis ball could theoretically diffract. However, we can show using the equation (lambda=h/p) that this is impossible in practice.-> At this point I would show why a tennisball doesn't diffract and an electron does diffract a lot more easily, using the equation. -> Then I would ask the student to explain it back to me so I can see how much they understood.