What are the characteristics of the three chief kinds of radiations that radioactive nuclei emit ?

The three important emanations from radioacdve nuclei are -

1. a - rays which are composed of helium nuclei.

2. 3 - rays which are streams of electrons.

3. 1( - rays which are electromagnetic radiations.

Their main properties may be summarised as follows.

a - rays Material particles - each particle is a helium nucleus - deflected by magnetic and electric fields - speed one-tenth of the speed of light penetrating power low due to heavy mass.

- rays :- Material particles - streams of electrons - deflected by magnetic and electric fields - speed very nearly that of light - high penetrating power.

- rays :- Electromagnetic radiations - speed that of light - unaffected by magnetic and electric fields - most dangerous and most penetrating.

2: a) If a radioactive nuclide of an alkaline earth element undergoes a - particle emission, in what group of the Periodic Table will the daughter element be found?

b) If a radioactive nuclide of group 15 element undergoes 3 - particle emission in what groupswill the daughter element be found

At!.s. a) When a radioactive elements emits an a - particle, the daughter element formed will have a mass number which is 4 units less than that of the parent, and an atomic number which is two units less than that of the parent. If the radioactive nuclide belongs to the family of alkaline earth metals, after loss of 2 units of atomic number, the daughter element formed will be a member of the family of noble gases (zero group).

b) Emission of i3 ray is accompanied by increase of one unit of atomic number without any change in mass number. Therefore the daughter element formed will be an isobar of the parent. If the radioactive parent belongs to Cr 15, the daughter element formed will belong to Gr 16.

What are the important properties of electromagnetic waves?

:Ans.: Some ofthe chief characteristics of electromagnetic waves are

(i) In electromagnetic waves, the directions ofoscillationnn ofthe electric and magnetic fields are perpendicular to each other as well as to the direction of propagation of the wave.

The speed of an em wave.in space is about 3 X 108 miS while in any other medium it depends on the electric and magnetic properties of the medium and not on the amplitude of the field variation.

The electric and magnetic field variations are in. phase, ie both attain theI maxima and minima at the same time and place.