Final answer:
To find m∠EDF, use the equation mẽ = qe/(a/vB) which gives the ratio of the charge of the electron to the deflection of the beam of electrons under a magnetic field.
Step-by-step explanation:
To determine the value of m∠EDF, we need to use the given equation Fmag = qevB = mẽ a. Here, Fmag represents the magnetic force, qe is the charge of the electron, v is the velocity of the electron, B is the magnetic field strength, and a is the deflection. By rearranging the equation, we can solve for mẽ: mẽ = qe/(a/vB). So, mẽ is the ratio of the charge of the electron to the deflection of the beam of electrons under a magnetic field.