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Showing posts from August, 2020
  Schools across state won’t reopen before Diwali: Maharashtra Govt. Mumbai: With Covid-19 positive cases showing no signs of slowing down in Maharashtra, the state government has decided to allow schools to reopen only after Diwali. This means children in over 1.2 lakh schools won’t be able to attend classes in person till November. Minister of School Education Varsha Gaikwad said the decision was taken after a meeting between her department and several school managements. Since schools are not ready to risk the lives of their students, the state has planned to push the reopening after Diwali, she said. Gaikwad said the Centre had sought the state government’s views about the resuming classes in schools for senior students. She said the Centre had also issued standard operating procedures or SOPs for the partial resumption of teaching activities in schools for students of Classes 9 to 12, on a voluntary basis, from September 21. Advertisement Advertisement “However, school managem...
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Solid state

 Solid state.                       Exercise. Q.no 1 :-   I) Molecular solids are....        a. Crystalline solid.    b. Amorphous solid.    c. Ionic solid.    d. Metallic solid.   II) which of the following is n-type semiconductor?    a. Pure Si.     b. Si doped with As.    c. Si doped with Ga.     d. Ge dopped with In. III) In Frenkel defect      a. Electrical neutrality of the substance is changed.     b. Density of the substance is changed.     c. Both cation and anion are missing.     d. Overall electrical neutrality is preserved. IV) In crystal lattice formed by bcc unit cell the void volume is    a. 68%    b. 74%     c. 32%    d. 26% V) The coordination number of atoms in bcc crystal lattice is   a. 2   b. 4   c. 6...
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Solid state

                   1. Solid state.  (Primitive/simple cubic unit cell):- -Has particles at its eight corners. -Each corner particle share's it's all seven parts to other unit cell to form crystal. -so, only 8th part comes under crystal. -So, 1/8×8 ( corner ) = 1 particle per unit cell. Body-centred cubic unit cell :- -In bcc unit cell, -[1/8th (part of single unit corner) × 8 + 1 × particle at body ] = 2 ( particles ) Face-centred cubic unit cell :- -In FCC,  -[1/8th (given unit cell at corner)× 8 + (1/2×6 face)] - [1+3] - 4 particle. Packing of particle in crystal lattice :- - Particles are closed packed in crystalline solid. - Always individual particle is treated as hard sphere. - The number of neighbouring spheres that touch any given sphere is its coordination number. -Magnitude of coordination number is measure of compactness of solid. - Larger the coordination number, the closer are the sphere to each other. 1) Close pac...
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Solid state.

    1. Solid state. Solid :  - solid  is the state of matter in which constituent particles are bonded with strong force of attraction. 1) Isomorphism :-  1) Two or more substances having the same crystal structure are said to be Isomorphism. 2) In these substances, the chemical composition has the same ratio. 2) Polymorphism :-  1) Single substance exist in two or more forms or crystalline structure is said to be polymorphism. 2) Polymorphs of structure formed in different conditions. 3) Example : Calcite and aragonite are two forms of calcium carbonate. 4) When it occur in element is called as allotropy. Classification of crystalline solids :- 1) Ionic solid -  1) Constituent particles are charged ions. 2) Both are bonded with each other by columb force. 3) Particles are held by electrostatics force of attraction. 4) They are hard/brittle with high melting point. 5) They are non-conductor at solid state and become good conductors when dissolved into ...
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Reproduction in lower and higher plants. Exercise

 Reproduction in lower and higher plants.                                                  Exercise Q. 2 Very short answer type questions : 1. Name the part of gynoecium that determines the compatible nature of pollen grain. ANS : stigma 2. How many haploid cells are present in a mature embryo sac ? ANS : An unfertilized embryo sac of angiosperm is composed of 7 cells i.e., 7-celled and 8-nuclei. Among 8-nuclei, 6 are enclosed by cell walls and are organized into cells, which are haploid in number - 3 antipodal, 2 synergids and 1 egg cell and a large central cell with 2 pollen nuclei. 3. Even though each pollen grain has 2 male gametes, why atleast 20 pollen grains are required to fertilize 20 ovules in a particular carpel? ANS : because only one male gamete is involved in syngamy or the fusion of male gamete with the egg cell. 4. Define megasporogenes...
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Reproduction in lower and higher plants. Part 5

 1. Reproduction in lower and higher plants.                                    Part 5 Dormancy :  Structural and physiological adaptive mechanism for survival is called Dormancy. Apomixis :  - Phenomenon of formation of embryo through asexual methods. - Gametophytic cell produces embryo without fertilization is called Apogamy. - Sporophytic cell produces embryo without fertilization is called Apospory. - Apomixis is divided into three parts : a) Recurrent Apomixis. b) Non-recurrent Apomixis. c) Adventive Embryony. A) Recurrent Apomixis :  The embryo sac generally rise either from an archesporial cell or form some other part of the nuclleus. B) Non-recurrent Apomixis : Megaspore mother cell undergoes usual meiotic division and a haploid embryo sac is formed. C) Adventive Embryony :  Embryos may develop from somatic nucellus or integuments along with normal zygotic em...
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Reproduction in lower and higher plants. Part 3

 Reproduction in lower and higher plants.                          Part 3....      Follow us for next part. Thank you....
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Reproduction in lower and higher plants. Part 2

 1. Reproduction  in lower and higher plants.                                    Part 2 Follow us for next part. Thank you...
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Reproduction in lower and higher plants. Part 1

 1. Reproduction in  lower and higher plants.                                     part 1 jQDfK6I/AAAAAAAAAA8/z6cCy_9bAnwpdJ2ZAipVPbIqgJRjw9ACgCNcBGAsYHQ/s1080/Screenshot_20200822-150902%257E2.png" style="margin-left: 1em; margin-right: 1em;"> Follow us for next part.  Thank you......
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