JEE PYQ: Atomic Physics Question 12
Question 12 - 2021 (18 Mar Shift 1)
A particle is travelling 4 times as fast as an electron. Assuming the ratio of de-Broglie wavelength of a particle to that of electron is 2 : 1, the mass of the particle is:
(1) $\frac{1}{16}$ times the mass of $e^-$
(2) 8 times the mass of $e^-$
(3) 16 times the mass of $e^-$
(4) $\frac{1}{8}$ times the mass of $e^-$
Show Answer
Answer: (4)
Solution
$\lambda = \frac{h}{p}$. $\frac{\lambda_p}{\lambda_e} = \frac{p_e}{p_p} = \frac{m_e v_e}{m_p v_p}$. $2 = \frac{m_e}{m_p} \cdot \frac{v_e}{4v_e}$. So $m_p = \frac{m_e}{8}$.
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