Positronium consists of an electron and a positron (same mass, opposite charge) orbiting round their common centre of mass. The broad features of the spectrum are therefore expected to be hydrogen-like, the differences arising largely from the mass differences. Predict the wavenumbers of the first three lines of the Balmer series of positronium. What is the binding energy of the ground state of positronium

Four identical lab carts each have a mass of 200 kg. different masses are added to the carts and the velocities are measured. all carts move to the right.

Anoche fuimos al restaurante el gusto. jaime le (1) (pedir) al camarero una mesa en la sección de no fumar. yo (2) (pedir) chuleta de cerdo con champiñones, papas y ensalada y jaime (3) (pedir) mariscos, arroz y ensalada. el restaurante estaba lleno (full) por eso no nos (4) (servir) muy rápido (very fast), pero la comida estaba deliciosa. no me lo vas a creer (you won't believe it) pero ¡jaime (5) (repetir) arroz y mariscos! ¡dos porciones (orders)! ¿ya entiendes por qué él no (6) (dormir) bien anoche?

Apropagating wave in space with electric and magnetic components. these components oscillate at right angles to each other. it may travel in a vacuum.