PLEASE HELP why is beta radiation used rather than alpha or gamma radiation in this paper thickness equipment?

Which tool is least in predicting weather

The bohr model of the atom explained why emission spectra are discrete. it could also be used to explain the photoelectric effect. which is a correct explanation of the photoelectric effect according to the model?

Type the letter that represents the correct location for each particle type below. the neutron is found at __ the electron is found at __ the proton is found at __