List of top Science Questions

(a) Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image of an object placed at a distance of 2F from such a lens. Mention the position and nature of the image formed. State the observable difference in the image obtained if the lens is uncovered. Give reason to justify your answer.
(b) An object is placed at a distance of 30 cm from the optical centre of a concave lens of focal length 15 cm. Use lens formula to determine the distance of the image from the optical centre of the lens.
A stomata closes when :
(i) it needs carbon dioxide for photosynthesis.
(ii) it does not need carbon dioxide for photosynthesis.
(iii) water flows out of the guard cells.
(iv) water flows into the guard cells.
The correct reason(s) in this process is/are :
Name the term used for the materials which cannot be broken down by biological processes. Give two ways by which they harm various components of an ecosystem.
A cross made between two pea plants produces 50% tall and 50% short pea plants. The gene combination of the parental pea plants must be
Give two reasons why some plants are grown by the method of vegetative propagation. List two methods used to grow plants vegetatively.
Draw a labelled diagram to show electrolytic refining of copper. State what happens when electric current is passed through the electrolyte taken in this case.
When a strip of aluminium metal is dipped in a solution of ferrous sulphate, the pale green colour of the solution fades away. State the conclusion you can draw from this observation. Write the chemical equation for the reaction that occurs in this case.
Name a plant growth hormone synthesized at the shoot tip. Explain its effect on the growth of a plant in response to light.
Assertion (A): Sex of the children will be determined by what they inherit from their mother. Reason (R): Women have XX sex chromosomes.

Write short notes on:
Mendel’s Laws

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Sex Determination

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Human Heart

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Photosynthesis

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Versatile Nature of Carbon

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Corrosion

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Micelle

Write IUPAC names of:
Acetic Acid

Write IUPAC names of:
Acetylene

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Heterotrophic nutrition

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Growth hormones in humans

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Geotropism in plants

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Ozone layer

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Ecosystem

Write one example on:
Budding

Write one example on:
Regeneration