Answer:
![B_x=-0.56 T](https://img.qammunity.org/2020/formulas/mathematics/high-school/4kcybad6x23nj12get3ew8d5z2i1uxkeu6.png)
Explanation:
We are given that an electron moves through a uniform magnetic field given by
![B=B_x\hat{i}+3..39 B_x\hat{j}](https://img.qammunity.org/2020/formulas/mathematics/high-school/rbb3z08ikylojo9s7fp30yjaqhbpqn5zky.png)
Velocity of electron=
m/s
Magnetic force acting on electron, F=
![4.22* 10^(-19) N](https://img.qammunity.org/2020/formulas/mathematics/high-school/i2j3ptsmindkvl1qkxqci6za2ozp98xds3.png)
We have to find
![B_x](https://img.qammunity.org/2020/formulas/mathematics/high-school/dwqxkzbuo4pq0z4dakxiqot86iewfeq3yk.png)
Charge on electron=q=
![-1.6* 10^(-19)C](https://img.qammunity.org/2020/formulas/physics/middle-school/z3nfekwouu5rf0hgugz32813xqcym50p7l.png)
We know that magnetic force on electron is given by
![F=q\vec{v}* \vec{B}](https://img.qammunity.org/2020/formulas/mathematics/high-school/og730ebhif6m33oqersz72b2dy70v8562e.png)
Substitute the value then we get
![4.22* 10^(-19)=-1.6* 10^(-19)(2.59\cdot 3.39B_x-4.09B_x)](https://img.qammunity.org/2020/formulas/mathematics/high-school/5he5fkktcn2zy09p8yivgzbn6i6htrwbq4.png)
![(8.7801B_x-4.09B_x)=(4.22* 10^(-19))/(-1.6* 10^(-19))](https://img.qammunity.org/2020/formulas/mathematics/high-school/j1vpu7wnmej0nebkk1tiq6pq1b330yapz0.png)
![4.6901B_x=-(4.22)/(1.6)](https://img.qammunity.org/2020/formulas/mathematics/high-school/25jrb1dpfr3um8zavv3n8uydnxh4yv3tzi.png)
![B_x=-(4.22)/(1.6* 4.6901)](https://img.qammunity.org/2020/formulas/mathematics/high-school/u8dieeovc2f7g7ltnsdx9jd8dho3fa60up.png)
![B_x=-0.56 T](https://img.qammunity.org/2020/formulas/mathematics/high-school/4kcybad6x23nj12get3ew8d5z2i1uxkeu6.png)