Question

The mass of a negative meson is 208 times the mass of electron. If e/m ratio of alpha particle is x unit ,the e/m ratio of this meson is: (a) x/208 unit (b) x/52 unit (c) 17.65x unit (d) 104x unit​

Answer 1

The mass of a negative meson is 208 times the mass of electron. e/m ratio of alpha particle is x unit.

To find : The e/m ratio of this meson is ...

solution : mass of meson, $m_m=208m_e$

we know, mass of alpha particle is four times the mass of proton.

i.e., $m_{\alpha}=4m_p$

but mass of proton is 1836 times the mass of electron.

so mass of alpha particle, $m_{\alpha}=4\times1836m_e$

charge on meson = 1e

charge on alpha particle = 2e

now e/m ratio of alpha particle = (2e)/(4 × 1836$m_e$) = x

⇒e/$m_e$ = 3672x ......(1)

e/m ratio of meson = (1e)/(208$m_e$)

= 1/208 × e/$m_e$

from equation (1) we get,

= 1/208 × 3672x

= 17.65x

Therefore the e/m ratio of meson is 17.65x