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

Momentum of the particle, `p=h/lambda=(6.63xx10^(-34))/(10^(-15))=6.63xx10^(-19)kgms^(-1)`
Rest mass energy `=m_(0)c^(2)=0.511xx1.6xx10^(-13)J`
Using relativistic formula for energy, we have
`E^(2)=c^(2)p^(2)+m_(0)^(2)c^(4)=(3xx10^(8))^(2)xx(6.63xx10^(-19))^(2)+(0.511xx1.6xx10^(-13))^(2) ~~9xx(6.63)^(2)xx10^(-22)`
As the second term (rest mass energy) is negligible small incomparison to the first term.
Therefore, `E=[9xx(6.63)^(2)xx10^(-22)]^(1//2)=1.989xx10^(-10)J =(1.989xx10^(-10))/(1.6xx10^(-19))eV=1.24xx10^(9)eV=1.24 BeV`
Thus the electron energies from the accelerator must have been of a few BeV.