Assuming that the difference between Thomsons calculated e/m in his second experiment (see Figure 3-19) and the

Question:

Assuming that the difference between Thomson’s calculated e/m in his second experiment (see Figure 3-19) and the currently accepted value was due entirely to his neglecting the horizontal component of Earth’s magnetic field outside the deflection plates, what value for that component does the difference imply? (Thomson’s data: B = 5.5 x 10^-4 T, ε = 1.5 x 10⁴ V/m, x₁ = 5 cm, y₂ /x₂ = 8/110.)

Figure 3-19