Question

You are working in a biotechnology company that specializes in the design of mass spectrometers with the team that develops the velocity selector. As part of the project design, you are in charge to solve the following problem. Molecules of mass 124u (u = 1.661×10−27 kg), have been ionized knocking out one electron, so its charge is ? = +?. The molecules, travelling horizontally, are accelerated until they reach a speed ?0 = 4.80 × 104 m/s, and then pass through a region between two horizontal electrode plates 2.50 cm long, separated a distance 2.00 cm. There is a vertical electric field of magnitude E pointing upwards, between the plates. After the molecules clear the region between the plates, they travel a horizontal distance ? = 1.50 cm (there is no electric field in this region) and must impact on a detector at vertical distance ℎ = 8.10 mm above the location they entered the plates (that is, the vertical displacement, from the time the molecules enter the region between the deflecting plates, until they hit the detector, is 8.10 mm). You must find the magnitude E of the electric field, to produce this result.

Make sure to:

• Draw a picture

• Include sufficient work.

• List any assumptions that may simplify the problem.

Answer 1

Calculation of deflecting electric field that is needed to make high speed ionized molecules reach the detector