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Eyes are the sense organs which give us the sense of vision. The human eye is almost spherical in shape. Following are the main structures in the human eye
Cornea: The eyeball is covered with a tough layer. This layer is transparent on the front. This transparent portion is called cornea.
Iris: Iris is a thin circular structure. It works like the shutter of a camera. It controls the amount of light entering the eye. The colour of iris imparts distinct colour to the eyes of an individual. A person with blue iris has blue eyes.
Pupil: There is a hole in the centre of iris. This is called pupil. Light enters the eye through the pupil. When the light is bright, iris contracts and thus allows less light into the eye. When the light is dim, iris dilates and thus allows more light into the eye.
Lens: Lens is present behind the pupil. The lens in the human eye is a convex lens. The size and thickness of the lens change as per the distance of an object.
Retina: Retina is at the back of the eye and marks the inner layer of the eyeball. Images are formed on the retina and thus it works like a screen. There are photosensitive cells in the retina. These cells are of two types, which are as follows:

Cone Cells: The cone cells are sensitive to bright light. They also give the sense of colour.
Rod Cells: The rod cells are sensitive to dim light.

Optic Nerve: The optic nerve emerges from the back of the eye ball. This nerve goes to the brain.
Blind Spot: The junction of retina and the optic nerve is called the blind spot. There is no photosensitive cell at this spot, and hence no image is formed at this spot on the retina.

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What are mole concept

Posted by Shivani Singh 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 3 months ago

A mole is defined as the amount of any chemical substance that contains as many elementary entities, e.g., atoms, molecules, ions, electrons, or photons, as there are atoms in 12 grams of pure carbon-12 (¹²C). Mole concept is one of the most convenient ways of expressing amount of reactants and product in reaction. The word “mole” was introduced around 1896 by Wilhelm Ostwald who derived the term from the Latin word moles meaning a ‘heap’ or ‘pile. The mass of one mole of substance is equal to the gram formula mass of that substance.

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What type of mixtures are separated by the technique of crystallization

Posted by Yassmain Saini 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Yogita Ingle 7 years, 3 months ago

Crystallisationis a process that separates a pure solid in the form of its crystals from a solution. The crystallisation method is used to purify solids. For example, the salt we get from sea water can have many impurities in it. To remove these impurities, the process of crystallisation is used.

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Shivani Singh 7 years, 3 months ago

By the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.

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a book has a mass of 400 grams find its weight when it is taken from the surface to a height equal to the radius of the earth

Posted by Vansh Shah 7 years, 3 months ago

CBSE > Class 09 > Science

0 answers

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Which is the simplest protective tissue present in animal body? State its 3 functions.

Posted by Srashti Patwa 5 years, 11 months ago

CBSE > Class 09 > Science

1 answers

Sheetal Thawani 7 years, 3 months ago

Epithelial tissue

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Relation between 'g' and'G'

Posted by Nishant Purbey 7 years, 3 months ago

CBSE > Class 09 > Science

3 answers

Ayush Middha 7 years, 3 months ago

g is acceleration due to gravity and G is gravitational constant

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Fathima Muhsin Muhsina 7 years, 3 months ago

g acceletation due to gravity G universal law

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Palak ?? 7 years, 3 months ago

g=MG/r*r

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How do we calculate number of electrons in an orbit

Posted by Priyanka Neupaney 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Palak ?? 7 years, 3 months ago

No. Of electrons in an atom is same as it's atomic no......no. of atoms in a shell can be found out by 2nsquare rule....let's take an example of neon....it's atomic no. Is 10...so it consist 10 electrons,...in its K shell...n=1 son by doing 2nsquare....2×1*1=2 so in Kshell three will be 2 electrons....in L shell n=2 so by rule no .of electrons in it are 8....so in this way 10 electrons of neon are distributed in different shells....but after L shell... remember that the two n Square rule is overlapped by octet rule

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What are the functions of mollusca

Posted by Harshita Jain 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Vandana Jaiswal 7 years, 3 months ago

Animals of this group are bilaterally symmetrical, triploblastic soft bodied but shelled with reduced coelomic cavity,open circulatory system and little segmentation. Body is differentiated into head ,foot and visceral mass covered by a special fold called mantle . Foot helps in movement. Respiration occurs by gills ,skinor lungs. Excretion is brought about by one or two pairs of sac like kidneys. Eyes and tentacles are present on head. Balancing as well as tasting organs are well developed. Sexes are separated larval stage present in its lifecycle.

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What is Avogadro,s

Posted by Amitabh Howlader 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Rishita Singh 7 years, 3 months ago

6.022×10^23

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Amitabh Howlader 7 years, 3 months ago

Avogadroo means it is a value 6.022 x10 to power 23

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Improvement in crop yields plese explain it

Posted by Aakriti Yadav 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 3 months ago

Following three scientific approaches are adopted in India to obtain high yield s from our agriculture farms:

Crop variety improvement
Crop production management
Nutrient management

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Anyone plz explain me what is magnitude?

Posted by Student Student 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Student Student 7 years, 3 months ago

Which type of value

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Paras Ramchandani 7 years, 3 months ago

Value

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Sir science m hindi notes available nhi h

Posted by Priya Sharma 7 years, 3 months ago

CBSE > Class 09 > Science

3 answers

Kharwil Gopiyani 7 years, 3 months ago

Wo Hindi English and Gujarati me available he

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Kharwil Gopiyani 7 years, 3 months ago

Online and library me sab kuch milta he ek bar library me jake science ki books padh.

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Anisha Vats 7 years, 3 months ago

I do not know???

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Whats full form of C

Posted by Yug - 7 years, 3 months ago

CBSE > Class 09 > Science

7 answers

Pratima Tiwari 7 years, 3 months ago

Kis subject mai

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Mehak Sharma 7 years, 3 months ago

Carbon

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Ayush Middha 7 years, 3 months ago

In chemistry , it is symbol of carbon

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Rishita Singh 7 years, 3 months ago

Carbon

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Anisha Vats 7 years, 3 months ago

Compressions(C)

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Harjap Singh 7 years, 3 months ago

In science carbon atomic number is 6

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Simran Kaur 7 years, 3 months ago

In sci. Its carbon..

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How to define wprk

Posted by Yug - 7 years, 3 months ago

CBSE > Class 09 > Science

4 answers

Palak ?? 7 years, 3 months ago

The act when one newton force acting on an object produces an acceleration of 1 M per second square this act is known as work

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Student Student 7 years, 3 months ago

Work is multiplicative unit of force applied to the displacement of the body.

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Simran Kaur 7 years, 3 months ago

Work is said to b done if a force is applied on the obj. And it displace from its origin point....may it help u....?

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Yug - 7 years, 3 months ago

Sory its work please answer me

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What are the components of natural resource

Posted by Tushar Jaiswal 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Vandana Jaiswal 7 years, 3 months ago

Air,water,soil,minerals,animals and plants

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ANSWER

Please derive it (Ek=½mv²)..???

Posted by Simran Kaur 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Simran Kaur 7 years, 3 months ago

Plzz do it guys....plzz....lets do all the ques together so we can help each other to doo all the ques. Easily... Do it naa...??

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Differentiate between isotopes and isobars

Posted by Sneha Baghel 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Rishita Singh 7 years, 3 months ago

Isotope - atomic no. of same element is same but mass no. is different. Isobars - mass no. of different elements is same but atomic no. is different.

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Plzz tell anyone....that F=???

Posted by Simran Kaur 7 years, 3 months ago

CBSE > Class 09 > Science

4 answers

Arpita Singh 7 years, 3 months ago

F=m×a

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Simran Kaur 7 years, 3 months ago

Thnkuu soo much gyuss...??

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Mehak Sharma 7 years, 3 months ago

Force = Mass× Acceleration

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Vijay Singh 7 years, 3 months ago

Force = Mass × Acceleration

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How to define

Posted by Yug - 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Mehak Sharma 7 years, 3 months ago

The movement of water molecules to the region of higher concentration to the region of lower concentration is called osmosis.

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Vishal Kumar Vishalgupta 7 years, 3 months ago

What is osmosis?

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Construction and working of sonar

Posted by Sahil Kumar 7 years, 3 months ago

CBSE > Class 09 > Science

0 answers

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Ch 14 natural resource the breath of life air defination

Posted by Shivam Kumar 7 years, 3 months ago

CBSE > Class 09 > Science

0 answers

ANSWER

Newton's law of gravitational?

Posted by Satadip Debnath 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Brahmesh Kumar 7 years, 3 months ago

Force is directly propotional to the mass of the objects and indirectly propotional to the distance between them.

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Difference between solute and solvent

Posted by Harshita Gupta 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Ananya Satapathy 7 years, 3 months ago

Solute is present in less amount Solvent is present in more amount

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What are air cavities

Posted by Lina Singh 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Ananya Satapathy 7 years, 3 months ago

Empty spaces filled with air are called air cavities

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Shruti Jaiswal 7 years, 3 months ago

Here cavities means spaces . That means spaces having air which makes them to experience buoyant force.

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When we only require diary animals and meat animals like cow,goat and chicken. Then how are other animals important for our usefulness?

Posted by Neena Sam 7 years, 3 months ago

CBSE > Class 09 > Science

1 answers

Sanika Deshmukh 7 years, 3 months ago

Other animal are also important as they give different types of eatables & many other things to us. Ex. Honeybee gives honey,wax etc.

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Name the microbes which cause malaria and kala azar

Posted by Mehak .. 7 years, 3 months ago

CBSE > Class 09 > Science

3 answers

Shruti Jaiswal 7 years, 3 months ago

Malaria is caused by a protozoan named plasmodium and Kala Azar is by a protozoan named Leishmania.

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Lina Singh 7 years, 3 months ago

Kala azar cause protozoa

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Neena Sam 7 years, 3 months ago

Leishmania

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Can an object have mechanical energy even if its momentum is 0? Explain

Posted by Arya Magade 7 years, 3 months ago

CBSE > Class 09 > Science

2 answers

Palak ?? 7 years, 3 months ago

Yes why not Mechanical energy is the sum of potential energy and kinetic energy since the momentum is zero that means that velocity is that means that velocity is zero because mass can never be zero of an object so kinetic energy become zero but potential energy have some value because it doesn't depend upon the velocity of an object so therefore there is some mechanical energy in an object even if its Momentum is zero....

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Mohit Gaur 7 years, 3 months ago

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What is immunisation? Please tell me ans. Fast tomorrow is my test.

Posted by Laxmikant Patel 7 years, 3 months ago

CBSE > Class 09 > Science