Question

A neutron, a proton, an electron and $\alpha$ -particle enters in a region of uniform magnetic field with equal velocities. The tracks of the particles are shown in figure. Relates the tracks to the particles.

• A. A-proton, B$-\alpha$particle, C-neutron,D electron
• B. A- $\alpha$ particle, B- proton, C-neutron, D-electron
• C. A- neutron, B$-\alpha$ particle, C - proton, D electron
• D. A-proton, B$-\alpha$ particle, C- electron, D - neutron

Answer 1

The correct option is A A-proton, B$-\alpha$particle, C-neutron,D electron

We know that force on charged particle Pn magnetic field is given by

$F=2(\overrightarrow{v}\times \overrightarrow{B})$

From Fleming's left hand rule, magnitude of force on positive charge will be leftwards and in negative charge is righwards.

So, track D is of electron

Pat C is undeviated. Therefore,

Path C is of neutron

among A anf B one of proton and other of $\alpha -$

Further,

$r=\frac{mv}{B_2}$ or $r\propto \frac{m}{2}$

Since,

${\left(\frac{m}{2}\right)}_{\alpha }>{\left(\frac{m}{2}\right)}_P$,

$\therefore r_{\alpha }>r_p$ so,

$\therefore$ Track B is of $\alpha -particle$

and

$\therefore$ Track A is of proton.

$\therefore$ option A is correct.