A proton and an electron moving with same kinetic energy enter uniform magnetic field at right- angle to its direction. The ratio of radii of their trajectories will be:
Answer & explanation
Correct answer: option 1
The correct answer is Option 1: 43 : 1
$r=\frac{\sqrt{2m \, K.E}}{qB}$, q is same for both electron and proton.
$⇒r ∝ \sqrt{m}⇒\frac{r_p}{m_e}=\sqrt{\frac{m_p}{m_e}}=\sqrt{\frac{1.67\times 10^{-27}}{9.1\times 10^{-31}}}$
$⇒\frac{r_p}{r_e}=\sqrt{\frac{m_p}{m_e}}$
Since, mₚ ≈ 1836 mₑ
rₚ / rₑ = √1836 / 1 ≈ 43 :1
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