Question

If a beam consisting of $\alpha ,\beta$ and $\gamma$ radiation is passed through an electric field perpendicular to the beam, the deflections suffered by the components in decreasing order are

• A. $\beta ,\gamma ,\alpha$
• B. $\beta ,\alpha ,\gamma$
• C. $\alpha ,\gamma ,\beta$
• D. $\alpha ,\beta ,\gamma$

Answer 1

The correct option is B $\beta ,\alpha ,\gamma$

The deflection of the beam depends on the acceleration due to the electric field in the direction perpendicular to the beam.

The acceleration due to electric field is given by,

$a=\frac{qE}{m}$

For $\beta$ particle, $q_{\beta }=e,m_{\beta }=m_e$

For $\alpha$ particle,

$q_{\alpha }=2e,m_{\alpha }\approx 4m_p\approx 4\left(1836m_e\right)$

$\Rightarrow a_{\beta }>>a_{\alpha }$

Therefore, the deflection of $\beta$ particle will be higher than the deflection of $\alpha$ particle.

As, $\gamma$ radiation has no charge, there will be no deviation.

Hence, option $\left(B\right)$ is correct.