Question

The diagram above shows atomic particles moving through a magnetic field.
A beam of electrons is deflected in the magnetic field and strikes at the point $P$ as shown in the figure.
At which letter would a stream of protons strike the screen?

• A. $A$
• B. $B$
• C. $C$
• D. $D$
• E. $E$

Answer 1

Answer: (D)

$D$

A proton has the charge opposite to that of electron so it will go in opposite direction of electron at point $D$ besides that direction of force on a charge $q$ can be determined by Fleming's left hand rule or by

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

if $\overrightarrow{v}$ is in $y$ direction ,$\overrightarrow{B}$ is in $x$ direction then $\overrightarrow{F}$ will be in $z$ direction

Further a proton is heavier than electron therefore its deflection will be smaller as compared to electron and proton strikes to point $D$ instead of point $E$.