Fig. 2.16 shows radiation entering a magnetic field into the page. Alpha particles and beta particles carry opposite charges, so they curve in opposite dire...
Question 1 Report
Fig. 2.16 shows radiation entering a magnetic field into the page. Alpha particles and beta particles carry opposite charges, so they curve in opposite directions along paths 1 and 3. 
The beta particles are deflected much more than the alpha particles by the same field. What is the main reason?
Answer Details
The correct answer is A (a beta particle has a much smaller mass than an alpha particle). In a magnetic field a charged particle moves on a circular arc of radius \( r = \frac{mv}{qB} \), so the smaller the mass \( m \), the tighter the curve and the greater the deflection. A beta particle is an electron with roughly \( \frac{1}{7000} \) of the mass of an alpha particle, so for the same field it is bent far more sharply along the strongly curved path.
Gamma radiation is uncharged and is not deflected at all, so it cannot push the beta particles sideways; a beta particle certainly does carry charge (it is negative); and nothing can move faster than light. The mass difference dominates over the fact that the alpha has the larger charge.
Download The App On Google Playstore
Everything you need to excel in your exams
