The document discusses two particle detectors: the Wilson cloud chamber and the Geiger counter. The Wilson cloud chamber uses supersaturated vapors to make the paths of ionizing particles visible, allowing their properties to be examined. It consists of a closed cylinder with a glass top and movable piston, containing a low-boiling liquid. In the Geiger counter, a potential difference is applied between a metal cylinder and central wire. When ionizing particles enter, they produce ions along their track which cause a discharge, detecting the particle. Alpha particles produce a thick track while beta particles produce a thin broken one, and gamma rays produce scattered dots.

1. Nuclear Radiations
NUCLEAR RADIATIONS
Qs. What do you know about Wilson and Cloud Chamber?
WILSON CLOUD CHAMBER
Introduction
Wilson Cloud Chamber is used to observe the path of ionizing particles.
It helps to examine the mechanism of ionization of various ionizing
radiations and the product of their interaction with material inside the
chamber.
Construction
It consist of a closed cylindrical chamber with transparent glass top “I”
and a movable piston on the bottom. On the sides near the top the
cylindrical is provided with a glass window for light and for the ionizing
particles or radiations. The piston can be moved up or down by a lever
attached to it. Before making the enclosed space above the piston
arright, enough quantity of a low boiling point liquid such as water or
alcohol is introduced in the space to produce its saturated vapours. A
small quantity of the liquid stay on the piston.
Working
The vapours of the liquid usually condense at its dew point but the
condensation never takes place in the absence of some particles, dust
particles or ions, which are essential to form the nuclei (centres) of
condensation. In particle free space the saturated vapour may cool
much below the dew point. Then they are called Super Saturated
Vapours. Paths, additional information about the charged and
uncharged nature, the magnitude of the charge, the charge to mass
ration (e/m), etc of the incident particle or the particle found by their
interaction with the atoms can be obtained. By this very method a
number of particles have been discovered.

2. Qs. Explain the construction and working of Gelger Counter.
Definition
Gelger counter is a portable device which is widely used for the
detaction of ionizing particles or radiations.
Construction
It consists of a hollow metal cylinder, one end of which is closed by an
insulating cap. At the centre of the cap is fixed a stiff straight wire
along the axis of the cylinder. A thin mica or glass disc closes the other
end which also serves as all entrance window for the ionizing particles
or radiations. The sealed tube usually contains a special mixture (air,
argon, alcohol etc) at a low pressure of 50 to 100 millimetres of
mercury. A potential difference of the order of one thousand volts is
applied between the metal cylinder and difference is only slightly less
than than, necessary to start a discharge between the wire and a
cylinder.
Working
When an ionizing particle enter the tube under this condition if a
charged particle pass through the chamber it produces ionization along
its track. The condensation of vapours takes place on ion in the form
of tiny droplets of fog, which can be photographed.
1. α-Particle
An α-particle is highly ionizing the ions produced are so numerous that
its trade is a thick and continuous line.
2. β-Particle
β-Particle is much less ionizing its track is therfore, a thin and broken
line.
3. γ – Rays
γ – Rays are photons emitted in a widening cone of some angle. They produce ionization
by photoelectric effect distributed on a wide space. Some of the photoelectrons ejected by

3. them give tiny line tracks in directions like the β- Particles and scattered dots are
produced. The γ – rays not produce well-defined line track.