Radius of curvature R = 30 cm

Radius of curvature = 2 × Focal length (f)

R = 2 f

Hence, the focal length of the given convex mirror is 15 cm.

Radius of curvature R = 30 cm

Radius of curvature = 2 × Focal length (f)

R = 2 f

Hence, the focal length of the given convex mirror is 15 cm.

Cause of heating effect of electric current: Electric current generates heat to overcome the resistance offered by the conductor through which it passes. Higher the resistance, the electric current will generate higher amount of heat. Thus, generation of heat by electric current while passing through a conductor is an inevitable consequence. This heating effect is used in many appliances, such as electric iron, electric heater, electric geyser, etc.

The most suitable method for preventing an iron frying pan from rusting is applying a coat of zinc. This is called galvanization. Grease and paint are also used for prevent rusting from iron. However, in case of iron frying pan, grease and paint cannot be applied because when fan will be heated and washed again and again, the coating of grease and paint would get destroyed.

Although solid ionic compounds are made up of ions but they do not conduct electricity in solid state. This is because in the solid ionic compound, the ions are held together in fixed positions by strong electrostatic forces and cannot move freely. However, when we dissolve the ionic solid in water or melt it, the crystal structure is broken down and ions become free to move and conduct electricity. Thus, an aqueous solution of an ionic compound conducts electricity because there are plenty of free ions in the solution which are able to conduct electric current.

Heterotrophic nutrition is the mode of nutrition in which an organism depends on other living organisms for food.

Depending on the type of food, heterotrophs can be divided into 3 types-

1. Carnivores- organisms which eat only animals. Example- lion, snake.
2. Herbivores- organisms which eat only plants. Example- rabbit, elephant.

Omnivores- organisms which eat both plants and animals. Example- crow, dog.

Heterotrophic nutrition is the mode of nutrition in which an organism depends on other living organisms for food.

Depending on the type of food, heterotrophs can be divided into 3 types-

1. Carnivores- organisms which eat only animals. Example- lion, snake.
2. Herbivores- organisms which eat only plants. Example- rabbit, elephant.

Omnivores- organisms which eat both plants and animals. Example- crow, dog.

The respiratory system is the network of organs and tissues that help you breathe. It includes your airways, lungs, and blood vessels. The muscles that power your lungs are also part of the respiratory system. These parts work together to move oxygen throughout the body and clean out waste gases like carbon dioxide

Focal length and radius of curvature:

• Let F be focus and C be center of curvature of a concave mirror.
• Consider an incident ray travelling parallel to principle axis and meet at point N.
• It passes through focus after reflection.
• CN is the normal drawn to the mirror(normals drawn to mirror meet at C).
• Now,

                   PC = R

                   PF = f

                   ∠FNC = ∠FCN = 

                  ∠MFN = 2

• In ΔMNC

                                   [For paraxial rays, M and P coincide]

• If  is small, 

                         ------------------------(1)

• In ΔMNF

                                   [For paraxial rays, M and P coincide]

• If  is small, 

                            ------------------------(2)

• Substituting (1) in (2), we get

                   2PF = PC

                       R = 2f

                        f = R/2

• Therefore, focal length is half the radius of curvature.

In fig, theta is taken instead of alpha.

Taking a concave mirror, the curved mirror will have a principal axis near which a ray of light is incident on the mirror parellel to it.

Now the angle between the radius of curvature and principal axis will be equal to the angle at which ray is incident and due to reflections law incident angle would be equal to angle cbf.

                                L abc = L cbf (law of reflection)

                                      L abc = L fcb ( alternate)

Hence, cbf = fcb ⇒ bf = fc

Since b very close to p; pf = fc ⇒ pc = 2 pf

Now considering convex mirror,  similar to concave mirror L abn = L nbd {reflection law}

L abn = Lbcf {corresponding}

Hence, bf = fc

Since, b is very close to p, pf = fc ⇒ pc = 2pf

Hence, in both cases Radius is double the focal length.

Structure of Nephron :-

Nephron is the filtration unit of kidney. It consists of a tubule which is connected with collecting duct at one end and a cup – shaped structure at the other end.

This cup-shaped structure is called ‘Bowman’s capsule’. Every Bowman’s capsule contains a cluster of capillaries, called ‘Glomerulus’, within the cup – shaped structure. The blood enters into Glomerulus through arteriole of renal artery.

Functioning of Nephron :-

1. Filtration: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and a major amount of water.

2. Re-absorption: As the filtrate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively re-absorbed into the blood by capillaries surrounding the nephron tubule.

The amount of water re-absorbed depends on the need of the body.

3. Urine: The filtrate which remains after re-absorption is called urine. Urine contains dissolved nitrogenous waste, i.e. urea and uric acid, excess salts and water. Urine is collected from nephrons by the collecting duct to carry it to the ureter.

Structure of a Nephrons:

• Nephrons are the basic filtering units of kidneys.
• Each kidney possesses large number of nephrons, approximately 1-1.5 million.
• The main components of the nephron are glomerulus, Bowman’s capsule, and a long renal tubule.

A n s w e r

The digestion process takes place in the following steps.

Ingestion

The very first step involves mastication (chewing). The salivary glands, along with the tongue, helps to moisten and lubricate food, before being pushed down into the food pipe.

Mixing and Movement

It involves the process of lubricating and manipulating food and pushing it down the food through the food pipe (using peristalsis), and into the stomach.

Secretion

The stomach, small intestine, liver, and pancreas secrete enzymes and acids to aid the process of digestion. It functions by breaking down food particles into simple components and easily absorbable components.

Digestion

The process of converting complex food particles into simpler substances in the presence of enzymes and acids secreted by different digestive organs.

Absorption

This process begins in the small intestine where most of the nutrients and minerals are absorbed. The excess water in the indigestible matter is absorbed by the large intestines.

Excretion

The process of removing indigestible substances and waste by-products from the body through the process of defecation.

In short, the digestion process consists of the six following steps:

Ingestion ⇒Mixing and Movement ⇒ Secretion ⇒ Digestion ⇒Absorption ⇒Excretion

The digestion process takes place in the following steps.

Ingestion

The very first step involves mastication (chewing). The salivary glands, along with the tongue, helps to moisten and lubricate food, before being pushed down into the food pipe.

Mixing and Movement

It involves the process of lubricating and manipulating food and pushing it down the food through the food pipe (using peristalsis), and into the stomach.

Secretion

The stomach, small intestine, liver, and pancreas secrete enzymes and acids to aid the process of digestion. It functions by breaking down food particles into simple components and easily absorbable components.

Digestion

The process of converting complex food particles into simpler substances in the presence of enzymes and acids secreted by different digestive organs.

Absorption

This process begins in the small intestine where most of the nutrients and minerals are absorbed. The excess water in the indigestible matter is absorbed by the large intestines.

Excretion

The process of removing indigestible substances and waste by-products from the body through the process of defecation.

In short, the digestion process consists of the six following steps:

Ingestion ⇒Mixing and Movement ⇒ Secretion ⇒ Digestion ⇒Absorption ⇒Excretion

Observations: Magnesium ribbon burns with dazzling light and white substance is formed which is magnesium oxide. This happens due to following chemical reaction:      2Mg(s)  + O2 (g) ====>  2MgO (s)

Results: Burning of magnesium in presence of oxygen to form magnesium oxide is a combination reaction.

The flame provides a source of heat so that the magnesium metal atoms can overcome their activation energy. Activation energy is the minimum energy required in order for a chemical reaction to proceed. When the magnesium metal burns it reacts with oxygen found in the air to form Magnesium Oxide.

• The first menstrual cycle begins at puberty but is not called menopause, instead it is called menarche. 
• Menarche is the first menstrual flow/discharge in female humans. Menopause marks the end of the menstrual cycle,

The correct option is (d) (B), (C) and (D).

•    Sodium sulphate chemically reacts with barium chloride in the form of their aqueous solution to form a white precipitate of barium sulphate. 

•    This is a double displacement reaction in which sulphate ions are displaced by chloride ions and vice-versa.

A n s w e r

Reaction of an alcohol with a carboxylic acid in presence of an acid to produce an ester is known as esterification reaction.

Reaction:

No, the size of the hole in the Ozone Layer has not been changed in recent year

Formation and depletion of the ozone is  a natural process and we can not control it.

What all we can do is to reduce the uses of CFC which are responsible for ozone hole.The problem is that the Cl radical which is released from CFC is responsible for the hole and while doing so this radicle is not consumed during the reaction and gets regenerated. In this way one Cl radical can destroy millions of ozone molecule. There are already a large amount of Cl radicals  in the stratosphere which are causing regular damage to the ozone layer and hence the ozone hole is not reducing even after putting so much regulations on uses of CFC.

No, the size of the hole in the Ozone Layer has not been changed in recent year

Formation and depletion of the ozone is  a natural process and we can not control it.

What all we can do is to reduce the uses of CFC which are responsible for ozone hole.The problem is that the Cl radical which is released from CFC is responsible for the hole and while doing so this radicle is not consumed during the reaction and gets regenerated. In this way one Cl radical can destroy millions of ozone molecule. There are already a large amount of Cl radicals  in the stratosphere which are causing regular damage to the ozone layer and hence the ozone hole is not reducing even after putting so much regulations on uses of CFC.

Wavelength is defined as the property of a wave in which the distance between the identical points between the two successive waves are calculated.

It is denoted by the Greek letter lambda (λ). Therefore, the distance between either one crest or trough of one wave and the next wave is known as wavelength.

The wavelength of light is defined as “The distance between the two successive crests or troughs of the light wave”.

1. Concentration in Parts Per Million (ppm)

The parts of a component per million parts (10⁶) of the solution.

ppm(A)=Mass of ATotal mass of the solution×106

2. Mass Percentage (w/w):

When the concentration is expressed as the percent of one component in the solution by mass it is called mass percentage (w/w). Suppose we have a solution containing component A as the solute and B as the solvent, then its mass percentage is expressed as:

Mass % of A = Mass of component A in the solutionTotal mass of the solution×100

3. Volume Percentage (V/V):

Sometimes we express the concentration as a percent of one component in the solution by volume, it is then called as volume percentage and is given as:

volume % of A = Volume of component A in the solutionTotal volume of the solution×100

For example, if a solution of NaCl in water is said to be 10 % by volume that means a 100 ml solution will contain 10 ml NaCl.

4. Mass by Volume Percentage (w/V):

This unit is majorly used in the pharmaceutical industry. It is defined as the mass of a solute dissolved per 100mL of the solution.

5. Molarity (M):

One of the most commonly used methods for expressing the concentrations is molarity. It is the number of moles of solute dissolved in one litre of a solution. Suppose a solution of ethanol is marked 0.25 M, this means that in one litre of the given solution 0.25 moles of ethanol is dissolved.

6. Molality (m):

Molality represents the concentration regarding moles of solute and the mass of solvent. It is given by moles of solute dissolved per kg of the solvent. The molality formula is as given-

Molality(m)=Moles of solute / Mass of solvent in kg

7. Normality

It is the number of gram equivalents of solute present in one liter of the solution and it is denoted by N.

N=Weight of solute in gramsEquivalent mass×Volume in liter

The relation between normality and molarity.

• N x Eq.Wt = Molarity x Molar mass
• N = Molarity x Valency
• N = Molarity x Number of H⁺ or OH^– ion

The buffer solution is a solution able to maintain its Hydrogen ion concentration (pH) with only minor changes on the dilution or addition of a small amount of either acid or base. Buffer Solutions are used in fermentation, food preservatives, drug delivery, electroplating, printing, the activity of enzymes, blood oxygen carrying capacity need specific hydrogen ion concentration (pH).

A neutralization reaction can be defined as a chemical reaction in which an acid and base quantitatively react together to form a salt and water as products.

Neutralization Reaction Examples

• Formation of Sodium Chloride (Common Salt):
  HCl + NaOH → NaCl + H₂O
• Titration methods using phenolphthalein.