Radioactivity :- Henry Becquerel discovered radioactivity in 1896 by accident. Experiments performed subsequently showed that radioactivity was a nuclear phenomenon in which an unstable nucleus undergoes a decay. Becquerel studying the fluorescence and phosphorescence of compounds irradiated with visible light, the observed an interesting phenomenon. After illuminating some pieces of uranium-potassium sulphate with visible light…
संक्रामक रोग :- वैसे रोग जो प्रत्यक्ष या अप्रत्यक्ष रूप से एक व्यक्ति से दूसरे व्यक्ति में फैलते हैं, उन्हें संक्रामक रोग कहते हैं| ऐसे रोग सूक्ष्मजीवों से होते हैं| सूक्ष्मजीव रोगी के शरीर में वृद्धि करते हैं और शरीर को रोग का आश्रय बना देते हैं| संक्रामक रोग के लक्षण :- शरीर के ताप…
अच्छे स्वास्थ्य की आवश्यक शर्तें निम्नलिखित हैं :- किसी व्यक्ति का स्वास्थ्य अच्छा तब होता है जब वह सभी प्रकार की बीमारियों से मुक्त हो एवं शारीरिक या मानसिक सभी कार्य प्रभावी ढंग से करता हो। अच्छे स्वास्थ्य की मूल शर्तें निम्नलिखित हो सकते हैं – 1. संतुलित आहार (Balanced diet) :- वैसा आहार जिसमें…
मलेरिया (Malaria) : मलेरिया एक संक्रामक रोग है जो प्रोटोजोआ समूह के सूक्ष्मजीव “प्लाज्मोडियम” के संक्रमण से उत्पन्न होता है। प्लाज्मोडियम की चार प्रजातियां होती है – मलेरिया कैसे फैलता है? इन कारणों से मलेरिया किसी मनुष्य के शरीर में फैलता है : मलेरिया के लक्षण (Symptoms of Malaria) : मलेरिया के लक्षण निम्नालिखित हैं…
Mass Defect and Nuclear Binding Energy :- The actual mass is always less than the sum of the individual masses of the constituent protons and neutrons because energy is removed when the nucleus is formed. This energy has mass, which is removed from the total mass of the original particles. This mass, known as the…
Isotopes :- These are atoms of the same elements having same atomic number but different mass number and neutrons number. Examples – ₁H¹, ₁H² and ₁H³ (protium) (deuterium) (tritium) are the Isotopes of hydrogen. Here deuterium oxide to form heavy water. Note – Tritium nuclei being unstable, do not occur naturally and are produced artificially…
Structure of Atomic Nucleus :- The atomic nucleus is the small, dense region consisting of protons and neutrons at the centre of an atom, discovered in 1911 by Ernest Rutherford based on the Geiger Marsden gold foil experiment. Proton :- A Proton is a subatomic particle, symbol ‘p‘ or p⁺ with a positive charge of…
Davisson and Germer Experiment :- The wave nature of electrons was first experimentally verified by C. J. Davisson and L. H. Germer in 1927 and independently by G. P. Thomson in 1928. The experimental arrangement consists of an electron gun which comprises of a tungsten filament ‘F’ , coated with barium oxide and heated by…
Mutation and Its Types:- Mutation is a phenomenon which results in alternation of DNA sequences and consequently results in changes in the genotype and phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads to variation in DNA. Causes of mutations :- There are many chemical and physical factors that induce…
Sex Determination in Human :- sex determination is a biological system that determines the development of sexual characteristic in an organism. Sex determination in human by chromosomal difference. Most organisms that created their offspring using sexual reproduction have two sexes. In human beings a sex chromosome that carries the genes for male characters is called…
मानव में लिंग निर्धारण (Sex determination in humans) :- मानव के प्रत्येक कोशिका में 23 जोड़े गुणसूत्र पाए जाते हैं जिसमें 22 जोड़े को अलिंग गुणसूत्र (Autosomes) तथा अंतिम 23वें जोड़ा को लिंग गुणसूत्र (Sex Chromosomes) कहते हैं। द्विगुणित अवस्था में मादा का लिंग गुणसूत्र XX तथा नर का लिंग गुणसूत्र XY होता है। मानव…
Crossing Over :- Crossing over is a mechanism by which a group of genes on one chromosome changes it’s place with a similar group on it’s homologous chromosome. Term crossing over were first given by Morgan & Castle in 1912. Mechanism of crossing over :- Mechanism can be explained under the following steps – 1….
