Fields D.3 Motion in Electromagnetic Fields (id: 34835db38)

本题目来源于试卷: Fields D.3 Motion in Electromagnetic Fields，类别为 IB物理学

[单选题]
A source of radiation is near a magnetic field that is directed into the page. A sheet of paper is placed in the path of the radiation before it enters the magnetic field.


The gamma radiation is not deflected when entering the magnetic field. Which of the following is correct about the other type of radiation that penetrates the paper sheet and the direction of its deflected path in the magnetic field?

A. Type of radiation is $α$ ; Direction of deflected path is Upwards
B. Type of radiation is $α$ ; Direction of deflected path is Downwards
C. Type of radiation is $β^-$ ; Direction of deflected path is Upwards
D. Type of radiation is $β^-$ ; Direction of deflected path is Downwards


参考答案:  D


本题详细解析:
Explanation:

The alpha, beta and gamma radiation have different penetrating powers, where alpha is the one with the least penetrating power and won’t pass through the paper sheet, while gamma and beta radiations will pass through the paper sheet.

When entering the magnetic field, gamma radiation will continue in its path without deflection because they have no charge. On the other hand, beta particles have negative charges, so they will be affected by a magnetic force that causes deflection in their path.

To determine the direction of the magnetic force, the right hand rule is used keeping in mind that the velocity direction in the right hand rule is that of a positive charge. So we have the direction of velocity is to the left, the magnetic field is into page, thus the magnetic force will be directed downwards.

*Any other hand-rule convention can also be used.

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