Answer:
![15.18* 10^(-9) m](https://img.qammunity.org/2020/formulas/physics/college/uwguqyki29qxn9rdo2s8nskm1m5meblu28.png)
Step-by-step explanation:
Radius of the path of electron which is moving perpendicular to magnetic field is defined as,
![r=(mv)/(qB)](https://img.qammunity.org/2020/formulas/physics/college/vpk58lkth2g609z17488yoe7xqgf1kafgq.png)
Here, m is the mass of electron, v is the velocity of electron, q is the charge on electron, and B is the magnetic field.
Given that, the velocity of electron is,
.
And the magnetic field is
.
And the mass of electron is,
![m=9.11*10^(-31)kg](https://img.qammunity.org/2020/formulas/physics/college/h19pqkbu89jdmg9axpki4xyj3uer6r2393.png)
And the charge on electron is,
![q=1.6* 10^(-19)C](https://img.qammunity.org/2020/formulas/physics/college/627f86um4qrbo0kigqe24z3ps2nzq5sswm.png)
Put all these values in radius equation,
![r=(9.11*10^(-31)kg* 4000m/s )/(1.6* 10^(-19)C* 1.5T)\\r=15.18* 10^(-9) m](https://img.qammunity.org/2020/formulas/physics/college/1hlgmtdl13t0pikl02wmjv6orc5rqxgd5z.png)
Therefore, the path radius of a moving electron is
![15.18* 10^(-9) m](https://img.qammunity.org/2020/formulas/physics/college/uwguqyki29qxn9rdo2s8nskm1m5meblu28.png)