Nature of image formed by spherical mirror = Real, inverted 
Magnification, m = -2 
Object distance, u=?
f=?
Image distance, v = -30 cm (-ve sign is for real image) 
\(m=\frac { -v }{ u } \)
\(\Rightarrow \frac { -v }{ u } =-2\)
\(\Rightarrow \frac { -30 }{ u } =2\)
2u=-30
∴ u=-15 cm
According to the mirror formula,
\(\frac { 1 }{ f } =\frac { 1 }{ v } +\frac { 1 }{ u } \)
\(\frac { 1 }{ f } =\frac { 1 }{ -30 } +\frac { 1 }{ -15 } \)
\(\Rightarrow \frac { 1 }{ f } =\frac { 1 }{ -30 } -\frac { 1 }{ 15 } =\frac { -1-2 }{ 30 } =\frac { -3 }{ 30 } \)
\(\frac { 1 }{ f } =\frac { -1 }{ 10 } \)
∴ f=-10cm
If the object is shifted 10 cm towards the mirror 
then, u = 15-10-5 cm 
In this case the object is placed between pole and focus of the spherical mirror. Therefore, the image formed is virtual, erect, magnified and behind the mirror.

The process by which new species develop from the existing species is known as speciation.
Factors leading to speciation:
(i)Geographical isolation of a population caused by various types of barriers like mountain ranges, rivers, sea etc. The geographical isolation leads to reproductive solation due to which there is no flow of genes between separated groups of population.
(ii)Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
(iii)Variations caused in individuals due to natural selection.
(iv)Drastic change in the genes or DNA called mutation is also a cause of speciation. Reproductive isolation cannot be major factor in the speciation of a self-pollinating
plant species. This is because, it does not depend on any other plant for its reproduction process.

The flow of energy in an ecosystem happens in following sequence:
Producer\(\rightarrow \) Primary Consumer\(\rightarrow \) Secondary Consumer\(\rightarrow \) Tertiary Consumer
The flow of energy is unidirectional in the food chain due to two reasons. A predator always eats its prey but other way round is not possible. Moreover, out of the total energy consumed by an organism at a particular trophic level; 90% is utilised for its own need and just 10% is left for the organism of next trophic level. Thus, the availability of energy gets reduced at subsequent trophic level. Due to this, the flow of energy is unidirectional in a food chain.

Carbon atoms have 4 electrons in their outcomes shell. So need to gain or lose electrons to attain noble gas configuration.
(i) It could gain four electrons forming c^4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
(ii) It could lose four electrons forming C⁴⁺ cations. But it would require a large amount energy to remove four electrons from its outermost shell.
Because of these reasons, carbon shares its valence electrons to complete its octet with other atoms to form covalent bonds.
(a) Covalent compounds are bad conductors of electricity because they do not contain ions.
(b) Covalent compounds have usually low melting and boiling because they are made up of electronically neutral molecule. So the force of attraction between the molecules of a covalent compound is very weak. Only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting and boiling points.

The following diagram depicts the pattern and direction of magnetic field lines around a straight current-carrying conductor.
Right Hand Thumb Rule: If a current carrying conductor is held by right hand, keeping the thumb straight and if the direction of electric current is in the direction of thumb, then the direction of wrapping of other fingers will show the direction of magnetic field.

At constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
Onh's law does not hold good under all conditions as it is not a fundamental law of nature like Newton's laws. It is obeyed by metallic conductors only when physical condition like temperature etc., are kept unchanged. It is not obeyed by a lamp filament.

The gas evolved at anode during electrolysis of brine is chlorine (G) When chlorine gas is passed through dry \(Ca(OH)_2\ (Y)\) produces bleaching powder (Z) used for disinfecting drinking water.
\(Ca(OH)_2+Cl_2\rightarrow CaOCl_2+H_2O\)
Since Y and Z are calcium salts, therefore X is also a calcium salt and is calcium carbonate.
\(CaCO_3+2HCl\rightarrow CaCl_2+CO_2+H_2O\)
\(Ca(OH)_2+CO_2 \rightarrow CaCO_3+H_2O\)

Neutral Salts : Potassium sulphate, sodium chloride
Basic Salts: Sodium carbonate 
Acidic Salts: Ammonium chloride

Defect-Myopia or short-sightedness Correction-Concave lens

Evolution shows that body design changed from simple to complex. Hence, bacteria has the simplest body design and chimpanzee has the most complex and better body design.

This is because, water does not provide energy to multiply whereas sugar provides energy for the yeast to undergo multiplication.

Thyroxine is the hormone secreted by the thyroid gland. This hormone regulates the metabolism of carbohydrates, fats and proteins. By regulating the metabolism it helps in optimum growth and development of the body.

Heat, light and electricity.

(a) According to Arrhenius theory, acids are substances that produce H⁺ ions when mixed with water.  On the other hand, based are substances that produce OH^- ions when mixed with water.
(b) NH₄OH is a weak base and HCl is a strong acid.

Biological magnification refers to the increase in the concentration of certain toxicants at each successive trophic level.
No, the levels of magnification will not be same in all trophic levels. When the chemicals do not get degraded and get accumulated progressively at each trophic level, it leads to biomagnification. It is more in organisms of higher trophic levels.

(i) Oxygen enters the human body through the nasal passage and reaches the lungs.
(ii) Numerous alveoli are present in the lungs. These alveoli are surrounded by many blood capillaries. From the alveoli, 0₂ is taken up by the red blood cells present in the blood capillaries.
(iii) Similarly, the CO₂ from the various tissues is transported to the alveoli.
(iv) This CO₂ is then released through the nasal passage during exhalation. Alveoli are the sites of exchange of gases. Each lung contains 300- 350 million alveoli.
These alveoli increase the surface area for gaseous exchange, making the process of respiration more efficient.

Haematite (Fe₂O₃) is an important ore of iron.
In the upper part of the blast furnace, carbon monoxide reduces iron (III) oxide to iron metal.
\(\underset { Iron(III)oxide }{ { Fe }_{ 2 }{ O }_{ 3 } } +\underset { Carbonmonoxide }{ 3CO(g) } \rightarrow \underset { Ironmetal }{ 2Fe(I) } +\underset { Carbondioxide }{ { 3CO }_{ 2 }(g) } \)
Following reactions are involved in the blast furnace:
(i) Formation of carbon monoxide
\(\underset { Carbon }{ C(s) } +\underset { Oxygen }{ { O }_{ 2 }(g) } \rightarrow \underset { Carbondioxide }{ { CO }_{ 2 }(g) } +Heat\\ \underset { Carbondioxide }{ { CO }_{ 2 }(g) } +\underset { Coke }{ C(s) } \rightarrow \underset { Carbonmonoxide }{ 2CO(g) } \)
(ii) Reduction of iron (III) oxide or haematite to iron
\(\underset { Iron(III)oxide }{ { Fe }_{ 2 }{ O }_{ 3 } } +\underset { Carbonmonoxide }{ 3CO(g) } \rightarrow \underset { Ironmetal }{ 2Fe(I) } +\underset { Carbondioxide }{ { 3CO }_{ 2 }(g) } \)

(a) A solar cell is a device which converts solar energy into electricity. It is a sandwich of a silicon-boron layer and a silicon-arsenic layer.
(b) Biogas is an ideal fuel for domestic use because it is a cheap and clean fuel, which does not leave behind any residue.
(c) A nuclear power plant is a device in which controlled chain reaction is used.

(a) Habitat, food, protection to wild life.
(b) Help in balancing CO₂ and O₂ of atmosphere.
(c) Improves water holding capacity of soil.
(d) Regulates water cycle
(e) For human being, they are the source for all essential commodities like, fuel wood, timber pulp and paper etc.
(f) It provides useful products like fruits, resins, gums, essential oils, bidi wrapper etc.

When the various elements were arranged in order of their increasing atomic masses, elements having similar properties fell under on another in the same vertical column called the group. He further observed that repetition of elements with similar physical and chemical properties occurred after certain regular intervals. On the basis of these observations, Mendeleev proposed his periodic law which states that the physical and chemical properties of elements are a periodic function of their atomic masses.