State the meaning of the de Broglie wavelength.
Calculate the de Broglie wavelength for an electron travelling at a speed of $4.9 \times 10^{7}\,\text{m s}^{-1}$.
State one way in which an electron and a positron are similar and one way in which they differ.
An electron moving at a speed of $4.9 \times 10^{7}\,\text{m s}^{-1}$ collides with a positron travelling at the same speed in the opposite direction. The collision produces two gamma-ray photons.
State the name given to this reaction.
State what happens to the electron and positron.
Explain why two gamma-ray photons are produced instead of only one.
Show that the electron’s kinetic energy before the collision is $1.1 \times 10^{-15}\,\text{J}$.
Use the information in d(i)v to determine, to three significant figures, the wavelength of the gamma radiation emitted in the collision.