A beam of alpha particle passes underflected with a horizontal velocity v, through a region of electric and magnetic fields, mutually perpendicular to each other and normal to the direction of the beam. If the mangnitude of the electric and magnetic fields are `120kVm^-1` and `60mT` respectively, calculate (i) velocity of the beam (ii) force with which it strikes a target on a screen, if the alpha particle beam current is equal to `1mA`? Mass of proton=mass of neutron `=1*675xx10^(-27)kg`.

Explanation

To solve the problem step by step, we will follow the instructions provided in the video transcript.

### Step 1: Calculate the Velocity of the Beam
Given:
- Electric field \( E = 120 \, \text{kV/m} = 120 \times 10^3 \, \text{V/m} \)
- Magnetic field \( B = 60 \, \text{mT} = 60 \times 10^{-3} \, \text{T} \)

For the beam to pass undeflected, the electric force must equal the magnetic force:
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