**Deflection of Alpha Particle in a Uniform Magnetic Field**

**Introduction:**
When a charged particle moves through a magnetic field, it experiences a force due to the interaction between its motion and the magnetic field. The direction of this force is perpendicular to both the velocity of the particle and the magnetic field. In this case, we have a uniform magnetic field directed vertically upwards and we need to determine the direction in which an alpha particle should be projected to be deflected southwards.

**Determining the Direction:**
To determine the direction in which an alpha particle should be projected, we need to consider the Lorentz force acting on the particle. The Lorentz force experienced by a charged particle moving in a magnetic field is given by the equation:

F = q(v x B)

where F is the force, q is the charge of the particle, v is the velocity of the particle, and B is the magnetic field.

**Right-Hand Rule:**
To determine the direction of the force acting on the alpha particle, we can use the right-hand rule. The right-hand rule states that if the thumb of the right hand points in the direction of the velocity of the charged particle and the fingers point in the direction of the magnetic field, then the palm of the hand will indicate the direction of the force acting on the particle.

**Applying the Right-Hand Rule:**
In this case, the alpha particle needs to be deflected southwards, which means the force acting on it should be directed towards the south. Since the magnetic field is directed vertically upwards, we can use the right-hand rule as follows:

1. Extend the right hand with the thumb pointing upwards to represent the velocity of the alpha particle.
2. Curl the fingers of the right hand in the direction of the magnetic field, which is vertically upwards.
3. The palm of the right hand will indicate the direction of the force acting on the alpha particle.

**Result:**
Using the right-hand rule, we find that the force acting on the alpha particle should be directed towards the east. Therefore, to achieve a deflection southwards, the alpha particle should be projected in the eastward direction.

**Conclusion:**
In conclusion, to deflect an alpha particle southwards in a uniform magnetic field directed vertically upwards, the alpha particle should be projected in the eastward direction. This can be determined using the right-hand rule, which helps us determine the direction of the force acting on a charged particle moving in a magnetic field.

It should be upwards.This direction can be determined by Fleming's left hand rule.