CBSE > Class 08 > Science | CBSE Board | Homework Help

Focal length is the distance between the centre of a lens or curved mirror and its focus.
A focus is the point where light rays originating from a point on the object converge.

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Whether coal and petroleum are exhastible natural resources

Posted by Sreekala K 6 years, 4 months ago

CBSE > Class 08 > Science

4 answers

Divyansh Sharma. 6 years, 4 months ago

Yes there are exhastible resources because they take million of years to be reformed as they are limited in amount

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Simran Choudhary 6 years, 4 months ago

yes they are exhastible natural resource

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Dilbagh Kumar 6 years, 4 months ago

Yes coal and petroleum are exhastible natural resources

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Dharmendra Kushwaha 6 years, 4 months ago

Yes they're

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What do you mean by Polymer

Posted by Adyasha Maharana 6 years, 4 months ago

CBSE > Class 08 > Science

8 answers

Ayushman Maurya 6 years, 4 months ago

Many small units combine to each other and made a large single unit is called apolymer

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Divyansh Sharma. 6 years, 4 months ago

many monomers join together to form larger unit called polymer

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Anik Kumar 6 years, 4 months ago

Polymer is a very big molecules which is formed by the arrangement of monomer

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Seema Gupta 6 years, 4 months ago

When the large monomer units are arrange they are known as polymer

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Hemant Kumar 6 years, 4 months ago

It is a type fibre

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Dharmendra Kushwaha 6 years, 4 months ago

A polymer is a long molecular structure usually consist of thousands of small molecular of monomer. Poly neans many and mer means chain. E.g glucose is monomer while starch is polymer.

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Yogita Ingle 6 years, 4 months ago

A polymer is a large molecule or a macromolecule which essentially is a combination of many subunits. The term polymer in Greek means ‘many parts’. Polymers can be found all around us. From the strand of our DNA which is a naturally occurring biopolymer to polypropylene which is used throughout the world as plastic.

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Aryan Raj 6 years, 4 months ago

Large molecule of various identical monomer units joined by some chemical bond in specific structure.

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Activity which show sound does not travel in vaccum

Posted by Abhijot Singh 6 years, 4 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 4 months ago

* Take a jar ,put an electric bell inside it .
* Create vacuum in it.
* Turn on the bell .
* You will notice that no sound can reach your ear.
This is because of the fact that sound needs a material medium to propagate.

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Define polymerisation

Posted by Abhi Morya 6 years, 4 months ago

CBSE > Class 08 > Science

3 answers

Divyansh Sharma. 6 years, 4 months ago

The process of joining of monomers to form polymer

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Seema Gupta 6 years, 4 months ago

The process of combining monomers into large polymer is known as polymerization

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Yogita Ingle 6 years, 4 months ago

A process of making the monomer molecules react together in a chemical reaction and produce three-dimensional networks or polymer chains is called polymerization.

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sound leson phy

Posted by Raji V 6 years, 4 months ago

CBSE > Class 08 > Science

1 answers

Ayush Aggarwal 6 years, 4 months ago

What is your question

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ANSWER

Define antibiotics

Posted by Manoj Bhardwaj 6 years, 4 months ago

CBSE > Class 08 > Science

7 answers

Ayushman Maurya 6 years, 4 months ago

A medicine which kill or stop the diseases causing microorganism is valled e antibiotic such as. Terramycin etc

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Divyansh Sharma. 6 years, 4 months ago

Antibiotics are chemical that kills Bacteria and it is use to treat several disease and penicillin was the first antibiotics that is discovered by Alexander Fleming

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Seema Gupta 6 years, 4 months ago

Antibiotic are the substance which kill or stop the growth of disease causing microorganisms.

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Santosh Ram 6 years, 4 months ago

a medicine which is used for destroying bacteria and curing infections

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Dharmendra Kushwaha 6 years, 4 months ago

Those medicine which are made from Bacteria and fungi and protect our body from those disease caused by microorganisms is called antibiotics. It was discovered by Alexander Fleming in 1928.

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Yogita Ingle 6 years, 4 months ago

Medicines which kill or stop the growth of the disease causing microorganisms are called antibiotics. The antibiotics are manufactured by growing specific microorganisms.
Example; Two important antibiotics are Tetracycline and Bacitracin.

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Manoj Bhardwaj 6 years, 4 months ago

These medicines to kill or stop the growth of the the disease causing microorganisms such medicines are called antibiotics

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How to do lab activity

Posted by V Srisanth 6 years, 4 months ago

CBSE > Class 08 > Science

1 answers

Somyak Mohanta 6 years, 4 months ago

By hands

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What is candle flame?

Posted by Tharini A L 6 years, 4 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 4 months ago

Candles produce light by releasing heat and all the turn on the candle produces come from a chemical reaction known as combustion in which wax reacts with oxygen in the air to produce carbon dioxide. The substances that vaporize while burning produces the flame. Kerosene oil and molten wax are the two substances that are responsible for producing flame while burning. Flame is defined as the area of combustion of a combustible substance. Substances that do not vaporize during burning, do not produce the flame.

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Define corrorion

Posted by Poonam Goswami 6 years, 4 months ago

CBSE > Class 08 > Science

2 answers

Ayush Aggarwal 6 years, 4 months ago

Corrosion is the wasting away of a metal

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Dharmendra Kushwaha 6 years, 4 months ago

Corrosion means rusting. Corrosion leads to the depletion of metal.

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ANSWER

Squeezing wet clothes for drying. 1.action? 2.efforts lead to force(yes/no) 3.does the effort involve an interaction betwen two objects(yes/no).

Posted by Nur Hasan 6 years, 4 months ago

CBSE > Class 08 > Science

1 answers

Aviral Chitransh 6 years, 4 months ago

2 yes 3 yes 1 ???

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What do you mean by endangered species

Posted by Meenaben Rathi 6 years, 4 months ago

CBSE > Class 08 > Science

4 answers

Tanushri Mehra 6 years, 4 months ago

The animals or birds or any other species which are left few in numbers and are going to be extinct are called endangered species.

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Ruhi Gaba 6 years, 4 months ago

the species which are in danger of extinction for example bat, tiger ,butterfly ,eagle ,snake.

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Lawanya Chandrakar? 6 years, 4 months ago

The species which are going to be extinct are called endemic species

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Ayesha Khatua 6 years, 4 months ago

Animal whose number are decreasing to the level that they might face extintion are known as endangered species.

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ANSWER

Who discovered antibiotics

Posted by Dunna Kushma 6 years, 4 months ago

CBSE > Class 08 > Science

6 answers

Suhani Singh 6 years, 4 months ago

Alexander Fleming

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Manoj Bhardwaj 6 years, 4 months ago

Alexander Fleming

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Dharmendra Kushwaha 6 years, 4 months ago

Alexander Flemming in 1928.

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Lawanya Chandrakar? 6 years, 4 months ago

Alexander fleming

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Vedant Patil 6 years, 4 months ago

Alexander Fleming

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Meenaben Rathi 6 years, 4 months ago

Alexander fleming

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ANSWER

What are irrigation

Posted by Kubodh Kumar 6 years, 4 months ago

CBSE > Class 08 > Science

6 answers

Seema Gupta 6 years, 4 months ago

The process of watering the plants at regular intervals is known as irrigation.

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Sreekala K 6 years, 4 months ago

The process of watering crops at regular intervel is called irrigation

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Dharmendra Kushwaha 6 years, 4 months ago

The process of supplying sufficient water to food crops is called irrigation.

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Aviral Chitransh 6 years, 4 months ago

Supply of water to crop is irrigation

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Ayesha Khatua 6 years, 4 months ago

The process of supply of water ?to the crop with regular interval is known an irrigation.

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Sarthak Jha 6 years, 4 months ago

The supply of water at regular intervals is called irrigation.

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What is the meaning of sperm?

Posted by Gourav Gorai 6 years, 4 months ago

CBSE > Class 08 > Science

4 answers

Gourav Gorai 6 years, 2 months ago

Thanx

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Aviral Chitransh 6 years, 4 months ago

Sperms are the reproductive cells of males and ova are the reproductive cell of females. Fusion of them causes formation of zygote. Zygote is further developed into an entire human being or any other organism

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Dharmendra Kushwaha 6 years, 4 months ago

Out of my brain

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Harsh Mishra 6 years, 4 months ago

Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a tot potent zygote. ... The word "sperm" is derived from the Greek word sperma (meaning"seed").

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What is theS.I unit of force and the solution..pls.

Posted by L Pausuanmung 6 years, 4 months ago

CBSE > Class 08 > Science

2 answers

Aadhurshini Rathinavel 6 years, 4 months ago

The S.I unit of force is newton represented by a symbol F. The S.I unit of solution is mol/kg.

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Dharmendra Kushwaha 6 years, 4 months ago

Force:- Newton Solution:- Mol

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What is the S.I unit of force?

Posted by L Pausuanmung 6 years, 4 months ago

CBSE > Class 08 > Science

5 answers

Sreekala K 6 years, 4 months ago

Newton(N)

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Lawanya Chandrakar? 6 years, 4 months ago

Newton

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Aviral Chitransh 6 years, 4 months ago

Newton

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Dharmendra Kushwaha 6 years, 4 months ago

Newton

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Kalyani Jaybhaye 6 years, 4 months ago

Newton

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What is nitrogen fixation name one microogranism which can doit

Posted by Pooja Meena 6 years, 4 months ago

CBSE > Class 08 > Science

3 answers

Seema Gupta 6 years, 4 months ago

Rhizobium

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Dharmendra Kushwaha 6 years, 4 months ago

The process of converting free nitrogen gas into nitrogen compound is called nitrogen fixation. N2+O2= 2NO 2NO+O2= 2NO2 4NO2+2NO2+O2= 4HNO3 CaO32+HNO2= Ca(NO3)2+ H2O+ CO2 One microorganisms is Rhizobium bacteria.

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Bellamkonda Surya Kiran 6 years, 4 months ago

Rhizobium,anaebena are some bacteria which can do nitrogen fixation

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For what purpose is a hoe used

Posted by Dev Khandelwal 6 years, 4 months ago

CBSE > Class 08 > Science