Educational blog

​ COLOURFUL WORLD   Rainbow Formation:-  It is a natural spectrum appearing in the sky after a rain shower. A rainbow is always formed in a direction opposite to that of the Sun. Three phenomena which are involved in rainbow formation are:- refraction dispersion and total internal reflection Atmospheric Refraction:-   The refraction of sunlight by different layers of atmosphere is called atmospheric refraction. Phenomena caused by atmospheric refraction:- Apparent position of star :-  The refractive index of earth’s atmosphere increases from top to bottom. So, the light coming from a star near the horizon has to travel from rarer to denser medium & it bends towards the normal. As a result the star appears higher than its actual position. Twinkling of stars:-  Since the physical conditions of the earth’s atmosphere are not constant, so the light from stars appears to come from different directions. This results in fluctuation of apparent position of star. Als...

​DIVISIBILITY RULES   A divisibility rule is a  shorthand and useful way of determining whether a given integer is divisible by a fixed divisor without performing the division, usually by examining its digits.

​MENSURATION FORMULAS

Periodic Trends of Properties of Elements In Periodic Table Modern periodic law is the base of periodic trends of properties of elements in the modern periodic table. Following properties of elements show a very clear periodic trend in the periodic table – Atomic Radius  Ionisation energy  Electron affinity  Electronegativity  Valence electrons  Valency  Metallic character of the elements  Non – metallic character of the elements  Reactivity of elements  Melting and boiling points of elements    Now, understand the trends of properties in detail by knowing the reason for the variation of properties.   Atomic Radius   Atomic radius is the distance between the centre of the nucleus of an atom to its outermost shell.    The periodic trend of atomic radius across a period – As we move from left to right in a period, atomic radius gradually decreases.   Reason – As we move left to right in a period the atomic n...

HUMAN RESPIRATORY SYSTEM 1) Nose: There is a pair of external nostrils at the lower end of nose.The air enters through the nostrils.The air passing through nostrils is filtered by fine hairs that lines the passage.The passage is lined with mucus which help in this process. 2) Throat or Pharynx : The nasal passage open behind into pharynx.It is a common passage for food and air.It leads into an air tube called trachea through a slit called  glottis .The glottis always remain open except during swallowing.The glottis bear a flap called  epiglottis .During swallowing epiglottis closes the glottis to avoid entry of food into air pipe. 3) Trachea : It is a thin walled tube that extends downwards through the neck and divides into 2 major bronchi.One major bronchi enters right lung and other left lung. 4) lungs : In humans,the respiratory organs are lungs which provide the surface for the exchange of gases.The lungs lie in the thoracic cavity on the sides of the heart. The thoracic c...