Answer: 20 pm=20*10^-12 m
Explanation: To solve this problem we have to use the relationship given by:
λmin=h*c/e*ΔV= 1240/60000 eV=20 pm
this expression is related with the bremsstrahlung radiation when a flux of energetic electrons are strongly stopped hitting to a catode. The electrons give their kinetic energy to the atoms of the catode.