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CBSE Class 10 Science Solved Question Paper 2014

Short Answer Type

31.

State with reason any two possible consequences of elimination of decomposers
from the Earth.

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32.

What is water harvesting? How can this technique help in the conservation of water?

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33.

Energy flow in a food chain is unidirectional. Justify this statement. Explain how the pesticides enter a food chain and subsequently get into our body.

1265 Views

34.

Write one difference between asexual and sexual mode of reproduction. Which species is likely to have better chances of survival - the one reproducing asexually or the one reproducing sexually? Justify your answer.

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35.

What is the effect of DNA copying, which is not perfectly accurate, on the reproduction process? How does the amount of DNA remain constant though each new generation in a combination of DNA copies of two individuals?

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36.

List three main factors responsible for the speciation and briefly describe each one of them.

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37.

A trait may be inherited, but may not be expressed. Justify this statement with the help of a suitable example

988 Views

Long Answer Type

38.

List two reasons for carbon forming a large number of compounds. Name the type of bonding found in most of its compounds. Why does carbon form compounds mainly by this kind of bonding? Give a reason why the carbon compounds.

(i) Generally, have low melting and boiling points.
(ii) do not conduct electricity in the molten state.

2074 Views

39.

(a) List the parts of the human eye that control the amount of light entering into it.

Explain how they perform this function.

(b) Write the function of retina in human eye.

(c) Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?

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40.
(a) Explain the following terms related to spherical lenses:

(i) optical centre
(ii) centres of curvature
(iii) principal axis
(iv) aperture
(v) principal focus
(vi) focal length

(b) A converging lens has focal length of 12 cm. Calculate at what distance the object should be placed from the lens so that it forms an image at 48 cm on the other side of the lens.

a) i) Optical centre: It is the central point of the lens. Optical centre is represented by O. When a ray of light passes through the optical centre, the ray of light does not suffer any deviation and goes straight.

ii) Centre of curvature: The centre of sphere of which a part of lens is formed is called the centre of curvature of the lens.

Concave and convex lens has two centre of curvature because they are formed by the combination of two parts of sphere. One centre of curvature is denoted by C₁ and second is denoted by C₂.

iii) Principal axis: The line passing through the optical centre of the lens and perpendicular to both faces of the lens is known as the principal axis.

iv) Aperture: Aperture is the diameter of the sphere of which a lens is formed.

v) Principal focus: The point at which a ray after refraction or reflection converges in a convex lens and mirror respectively is known as the principal focus.

The point at which an incident ray after refraction or reflection appears to diverges on the principal axis in a concave lens and concave mirror is known as principal focus.

vi) Focal length: The distance between the optical centre and principal focus of the lens is known as the focal length.

b) Given that,

Image distance, v = +48 cm

Focal length, f= +12 cm

Object distance, u = ?

Now, using the lens formula,