A student used paper chromatography to investigate the colours in different inks. Figure 1 shows the apparatus the student used.

The student made two mistakes in setting up the apparatus. Identify the two mistakes. Describe the problem each mistake would cause.

The nuclear potential that binds protons and neutrons in the nucleus of an atom is often approximated by a square well. imagine a proton conned in an innite square well of length 105 nm, a typical nuclear diameter. calculate the wavelength and energy associated with the photon that is emitted when the proton undergoes a transition from the rst excited state (n 2) to the ground state (n 1). in what region of the electromagnetic spectrum does this wavelength belong?