J.J. Thomson is best known for his discoveries about the nature of cathode rays.

Question

J.J. Thomson is best known for his discoveries about the nature of cathode rays. His other important contribution was the invention, together will one of his students, of the mass spectrometer, a device that measures the ratio of mass m to (positive) charge q of an ion. This spectrometer consists of two regions as shown in the figure in the first region an electric field accelerates the ion follows a circular are in a magnetic field. The radius of curvature of the are can be measured and then the m/q ratio can be found. After being accelerated to a speed of 1.5 Times 10^5 m/s. the particles enters a uniform magnetic field of strength 0.500 T and travels in a circle radius 33.0 cm (determined by observing where it the screen as shown in the figure). The results of this experiment allow one to find m/q. Find the radio m/q for this particle. Express your answer numerically in kilograms per coulomb.

Explanation / Answer

As the image is a bit blured speed seems to be what i have taken, if the value is different let me know.
speed of particle , v = 1.5 *10^5 m/s
magnetic field , B = 0.9 T
radius r = 0.33 m

Magnetic Force, F = q*v*B
This Fore = Centripetal Force
q*v*B = mv^2/r
q*B = m*v/r
r*B/v = m/q
m/q = (0.33*0.9)/(1.5 *10^5)
m/q = 1.98 * 10^-6 Kg/C

Ratio m/q is = 1.98 *10^-6 Kg/C

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