Download Deflection of Beta Particles in Magnetic Field

Experiment 8
Deflection of Beta Particles in Magnetic Field
Objective:
To deflect the path of β radiation by means of magnetism.
Theory:
Any charged particle moving through a magnetic field will
experience a force. The force will be perpendicular to the directions of
both the magnetic field and the velocity of the charged particle. The
Lorentz force can be written as:
(1)
If θ is the angle between υ and B, equation (1) can be written as:
(2)
If the particle has a negative charge, as does a conventional Beta particle,
the force will be in the opposite direction from that experienced by the
positive charged particle.
When the magnetic field remains constant, it will continue to experience
this constant force perpendicular to the velocity vector. This force to
change the direction of charged particles and follow a circular path at
constant velocity in the magnetic field. So that the magnetic field cause
Beta particles to change direction as the particles cross this field.
Apparatus:
Deflection chamber with plate capacitor.
DC power supply unit.
Voltameter.
Coils.
1
Prepared By Najat AL-Twarqi
Counter.
Geiger detector.
Slide angle scale.
Beta source.
Stopwatch.
Connecting leads.
Procedure:
1- Connect the apparatus as shown in Fig.1.
2- At current ( I ) equal zero change the angle (-200,…,00,…,400) and
record the number of count (n) per 100 s at each angle.
3- Increase the current to 0.5mA and repeat step2.
4- Calculate the count rate (n/100s).
5- Plot a graph between the angle θ and the count rate per 100 s
(n/100s).
Fig.1
2
Prepared By Najat AL-Twarqi
Results:
I (mA)
θ0
0
20
10
0
10
20
30
40
20
10
0
10
20
30
40
0.5
n (count/s)
for t=100 s
n/100 (s-1)
n/100 (s-1)
I=0
I = 0.5 mA
-20
-10
0
10
20
30
40
θ0
Fig.2
3
Prepared By Najat AL-Twarqi