Q. An infinitely long line of charge has linear charge density 4.00 10-12 C/m. A proton (mass 1.67 10-27 kg, charge +1.60 10-19 C) is 17.0 cm from the line and moving directly toward the line at 3000m/s. How close does the proton get to the line of charge?

Q. Two stars are 4.30 1011 m apart and are equally distant from the earth. A telescope has an objective lens with a diameter of 1.10 m and just detects these stars as separate objects. Assume that light of wavelength 550 nm is being observed. Also assume that diffraction effects, rather than atmospheric turbulence, limit the resolving power of the telescope. Find the maximum distance that these stars could be from the earth.