question_answer

In the experiment for the determination of \[\frac{e}{m}\]of electrons by the Thomson method, electric and magnetic fields are

A)  parallel and both are perpendicular to the motion of the electron

B)  both mutually perpendicular and parallel to the motion of electron

C)  both mutually perpendicular and also perpendicular to the motion of electron

D)  both mutually perpendicular and have no relation with motion of the electron

Correct Answer: C

Solution :

In Thomson's .experiment to determine the  charge to mass ratio of an electron, his apparatus was as follows: A uniform magnetic field is created between X and Y, by applying a potential difference  between them. In the same region and outside the tube is placed an electromagnet which produces a magnetic field perpendicular to the plane of paper. Thus, two fields are produced in the same region perpendicular to each other, also the two fields are perpendicular to the motion of electron.