10th class physics natural radio activity,back ground radiation,cosmic r...

NATURAL
RADIOACTIVITY

Definition:

The spontaneous emission of radiation by
unstable nuclei is called natural radioactivity. And the elements which emit
such radiations are called radioactive elements.

Unstable
nuclei

Unstable nuclei are those nuclei whose
atomic number is greater than 82.Some isotopes are also unstable.

Discovery
of Radioactive elements:

In 1896, Becquerel accidentally
discovered that uranium salt crystals emit an invisible radiation that can
darken a photographic plate.

Henrey
Becquerel suggested that radioactivity was the result of the decay or
disintegration of unstable nuclei 

Marie Curie and her husband Pierre
discovered two new elements which emitted radiations. These were named polonium
and radium.

 This process of emission of radiations by some
elements was called natural radioactivity by Marie Curie.

BACKGROUND
RADIATIONS

Definition:

Radiations
present in atmosphere due to different

radioactive substances are called background radiations

Explanation:

Everywhere in rocks, soil, water, and air
of our

planet are traces of radioactive elements. This natural radiation is called the
background radiation.

It is as much part of our environment as
sunshine and rain.

 Fortunately, our bodies can tolerate it. Only
places where radiation is very high can be injurious to health.

Cosmic
radiation

Definition:

The Earth, and all living things on it
also receive radiation from outer space. This radiation is called cosmic
radiation

Explanation:

It primarily consists of protons,
electrons, alpha particles and larger nuclei.

The
cosmic radiation interacts with atoms in the atmosphere to create a shower of
secondary radiation, including X-rays, muons, protons, alpha particles,
electrons, and neutrons