The wavelength of a probe is roughly a measure of the size of structure that it can probe in some detail. The quarks structure of photons and neutrons appears at the minute length -scale of `10^(-15)m` or less. This structure was first probed in early 1970's using high energy electron beam produced by a linear accelerator at Stanford's USA. Guess what might have been the order of energy of these electron beams (Rest mass energy of electron=0.511 eV).

Explanation

Given `lambda = 10^(-15) m , E = 0.511 MeV , P = h/lambda = (6.63 xx10^(-34))/(10^(-15)) = 6.63 xx10^(-19) " Kg"^(-m//s)`
Rest mass energy `E_(0) = m_(0)c^(2) = 0.511 MeV = 0.511 xx 1.6 xx 10^(-13) T`
From relativstic theory , `E^(2) = p^(2)c^(2) + m_(0)^(2)c^(4)`
` = (3 xx 10^(8) xx 6.63 xx 10^(-19))^(2) + (0.511 xx 10^(-13)xx 1.6)^(2) = 9 xx (6.63 )^(2) xx10^(-22)`
As the rest mass energy is negligible ` :. ` Energy E = ` sqrt(p^(2)c^(2) ) = pc = 6.63 xx10^(-19) xx 3xx 10^(8)`
` = (1.989 xx10^(-10))/(1.6 xx10^(19)) eV = 1.24 xx10^(9) eV = 1.24 " BeV"`
Thus , the energies the electron beam , the energy should be of the order of BeV.