▶️ Answer/Explanation
The process by which a green plant absorbs light energy and produces glucose is called photosynthesis, which is a form of nutrition.
Nutrition is the characteristic of living things concerned with obtaining materials needed for energy and building materials — photosynthesis is the plant’s way of making its own food.
The other options are incorrect: respiration releases energy from glucose; excretion removes waste; growth increases in size.
✅ Answer: (C)
Nutrition is the characteristic of living things concerned with obtaining materials needed for energy and building materials — photosynthesis is the plant’s way of making its own food.
The other options are incorrect: respiration releases energy from glucose; excretion removes waste; growth increases in size.
✅ Answer: (C)
▶️ Answer/Explanation
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration.
A greater concentration gradient means there is a larger difference in concentration between the two regions, so particles diffuse more rapidly — the rate of diffusion increases.
The graph in option D shows a straight-line increase in rate as concentration gradient increases, which correctly represents this directly proportional relationship.
✅ Answer: (D)
A greater concentration gradient means there is a larger difference in concentration between the two regions, so particles diffuse more rapidly — the rate of diffusion increases.
The graph in option D shows a straight-line increase in rate as concentration gradient increases, which correctly represents this directly proportional relationship.
✅ Answer: (D)
▶️ Answer/Explanation
Proteins are made of amino acids, which always contain the elements carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
Unlike carbohydrates and lipids, proteins always contain nitrogen as part of their amino group \((-\text{NH}_2)\), making nitrogen the key distinguishing element.
Some proteins also contain sulfur, but nitrogen is the essential element present in all proteins that distinguishes them from carbohydrates and fats.
✅ Answer: (C)
Unlike carbohydrates and lipids, proteins always contain nitrogen as part of their amino group \((-\text{NH}_2)\), making nitrogen the key distinguishing element.
Some proteins also contain sulfur, but nitrogen is the essential element present in all proteins that distinguishes them from carbohydrates and fats.
✅ Answer: (C)
▶️ Answer/Explanation
At high temperatures, the bonds holding the enzyme’s tertiary structure are broken — this is called denaturation (statement 3 is correct).
Denaturation causes the active site to change shape so it is no longer complementary to the substrate (statement 2 is correct).
Statement 1 is incorrect because at high temperatures particles actually move faster and collide more frequently — it is the changed active site shape (not fewer collisions) that prevents the enzyme from working.
✅ Answer: (D)
Denaturation causes the active site to change shape so it is no longer complementary to the substrate (statement 2 is correct).
Statement 1 is incorrect because at high temperatures particles actually move faster and collide more frequently — it is the changed active site shape (not fewer collisions) that prevents the enzyme from working.
✅ Answer: (D)
▶️ Answer/Explanation
Magnesium ions (\(\text{Mg}^{2+}\)) are an essential component of the chlorophyll molecule; without them, plants cannot produce chlorophyll and leaves turn yellow — a condition called chlorosis.
The yellowing appears between the veins (interveinal) because the veins themselves still have some green tissue, and it starts in older leaves because magnesium is a mobile nutrient that gets moved to younger growing leaves first.
Lack of sunlight or carbon dioxide would reduce photosynthesis but not cause this specific yellowing pattern; water deficiency causes wilting rather than interveinal yellowing.
✅ Answer: (B)
The yellowing appears between the veins (interveinal) because the veins themselves still have some green tissue, and it starts in older leaves because magnesium is a mobile nutrient that gets moved to younger growing leaves first.
Lack of sunlight or carbon dioxide would reduce photosynthesis but not cause this specific yellowing pattern; water deficiency causes wilting rather than interveinal yellowing.
✅ Answer: (B)
▶️ Answer/Explanation
Statement 1 is correct: a lack of vitamin C causes scurvy (bleeding gums, poor wound healing). Statement 2 is correct: a lack of vitamin D causes poor calcium absorption leading to softening/weakening of bones (rickets in children).
Statement 3 is incorrect: kwashiorkor is caused by protein deficiency, not calcium deficiency. Statement 4 is incorrect: marasmus is caused by overall energy/calorie deficiency, not iron deficiency (iron deficiency causes anaemia).
✅ Answer: (A)
Statement 3 is incorrect: kwashiorkor is caused by protein deficiency, not calcium deficiency. Statement 4 is incorrect: marasmus is caused by overall energy/calorie deficiency, not iron deficiency (iron deficiency causes anaemia).
✅ Answer: (A)
▶️ Answer/Explanation
Xylem vessels are formed from cells that have died, leaving hollow tubes with lignified walls — they are therefore dead structures, which eliminates options A and B.
Xylem transports water and dissolved mineral ions from roots to leaves, which is part of the transpiration stream — not translocation (translocation is the movement of sugars through phloem).
This confirms option D: xylem vessels are dead and involved in transpiration.
✅ Answer: (D)
Xylem transports water and dissolved mineral ions from roots to leaves, which is part of the transpiration stream — not translocation (translocation is the movement of sugars through phloem).
This confirms option D: xylem vessels are dead and involved in transpiration.
✅ Answer: (D)
▶️ Answer/Explanation
The word equation for aerobic respiration is: \(\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}\).
Glucose and oxygen are the reactants (used), while carbon dioxide and water are the products (produced).
The correct row in the table must show oxygen as used and carbon dioxide + water as produced, which corresponds to option B.
✅ Answer: (B)
Glucose and oxygen are the reactants (used), while carbon dioxide and water are the products (produced).
The correct row in the table must show oxygen as used and carbon dioxide + water as produced, which corresponds to option B.
✅ Answer: (B)
▶️ Answer/Explanation
A motor neurone has a cell body at one end with many short dendrites, and a long axon leading to an effector (muscle or gland); the diagram shows this structure with the cell body near the spinal cord.
Impulses in a motor neurone travel from the CNS to the effector, i.e. away from the cell body along the axon.
This matches option A: motor neurone, with impulses travelling from P to Q (from CNS towards the effector).
✅ Answer: (A)
Impulses in a motor neurone travel from the CNS to the effector, i.e. away from the cell body along the axon.
This matches option A: motor neurone, with impulses travelling from P to Q (from CNS towards the effector).
✅ Answer: (A)
▶️ Answer/Explanation
Body (somatic) cells of tigers are diploid with 38 chromosomes; gametes (sperm and egg) are produced by meiosis and are haploid, containing \(\frac{38}{2} = 19\) chromosomes each.
At fertilisation, a sperm (19 chromosomes) fuses with an egg (19 chromosomes) to form a zygote with \(19 + 19 = 38\) chromosomes, restoring the diploid number.
The correct row therefore shows: gametes = 19, zygote = 38, which corresponds to option C.
✅ Answer: (C)
At fertilisation, a sperm (19 chromosomes) fuses with an egg (19 chromosomes) to form a zygote with \(19 + 19 = 38\) chromosomes, restoring the diploid number.
The correct row therefore shows: gametes = 19, zygote = 38, which corresponds to option C.
✅ Answer: (C)
▶️ Answer/Explanation
Since the parents have an affected child but are unaffected themselves, both parents must be carriers with genotype \(Aa\) (where \(a\) = cystic fibrosis allele).
The cross \(Aa \times Aa\) gives offspring in the ratio \(AA : Aa : Aa : aa = 1:2:1\), so the probability of the homozygous recessive genotype \(aa\) (affected) is \(\frac{1}{4} = 25\%\).
Each pregnancy is an independent event, so the chance of the next child having cystic fibrosis remains 25% regardless of previous children.
✅ Answer: (B)
The cross \(Aa \times Aa\) gives offspring in the ratio \(AA : Aa : Aa : aa = 1:2:1\), so the probability of the homozygous recessive genotype \(aa\) (affected) is \(\frac{1}{4} = 25\%\).
Each pregnancy is an independent event, so the chance of the next child having cystic fibrosis remains 25% regardless of previous children.
✅ Answer: (B)
▶️ Answer/Explanation
A herbivore is an organism that feeds exclusively on plants, making it a primary consumer in a food chain.
Carnivores feed only on animals; producers (plants) make their own food through photosynthesis; secondary consumers eat primary consumers (not plants directly).
The definition “obtains energy by feeding only on plants” is the precise definition of a herbivore.
✅ Answer: (A)
Carnivores feed only on animals; producers (plants) make their own food through photosynthesis; secondary consumers eat primary consumers (not plants directly).
The definition “obtains energy by feeding only on plants” is the precise definition of a herbivore.
✅ Answer: (A)
▶️ Answer/Explanation
Trees remove \(\text{CO}_2\) and produce \(\text{O}_2\) through photosynthesis: \(\text{CO}_2 + \text{H}_2\text{O} \xrightarrow{\text{light}} \text{glucose} + \text{O}_2\). Deforestation drastically reduces the number of trees performing photosynthesis.
With fewer trees photosynthesising, less \(\text{CO}_2\) is removed from the atmosphere and less \(\text{O}_2\) is added — so atmospheric \(\text{CO}_2\) increases and \(\text{O}_2\) decreases.
Additionally, burning or decomposition of felled trees releases stored carbon as \(\text{CO}_2\), further increasing its atmospheric concentration.
✅ Answer: (C)
With fewer trees photosynthesising, less \(\text{CO}_2\) is removed from the atmosphere and less \(\text{O}_2\) is added — so atmospheric \(\text{CO}_2\) increases and \(\text{O}_2\) decreases.
Additionally, burning or decomposition of felled trees releases stored carbon as \(\text{CO}_2\), further increasing its atmospheric concentration.
✅ Answer: (C)
▶️ Answer/Explanation
Iron rusting forms a new substance — iron oxide \((\text{Fe}_2\text{O}_3)\) — and is irreversible, so it is a chemical change. Burning coal produces \(\text{CO}_2\) and \(\text{H}_2\text{O}\) as new substances, also an irreversible chemical change.
Dissolving sugar in water is a physical change — the sugar can be recovered by evaporation and no new substance is formed. Boiling water is also a physical change — only the state changes from liquid to gas, and no new substance is produced.
✅ Answer: (A)
Dissolving sugar in water is a physical change — the sugar can be recovered by evaporation and no new substance is formed. Boiling water is also a physical change — only the state changes from liquid to gas, and no new substance is produced.
✅ Answer: (A)
▶️ Answer/Explanation
Covalent bonds form when two non-metal atoms share electrons — so covalent compounds are composed of non-metals only (e.g. \(\text{H}_2\text{O}\), \(\text{CO}_2\), \(\text{CH}_4\)).
Simple covalent molecules have weak intermolecular forces between molecules, meaning only a small amount of energy is needed to overcome them — they therefore have low melting points.
The correct row shows: non-metals forming covalent bonds + low melting point, which is option C.
✅ Answer: (C)
Simple covalent molecules have weak intermolecular forces between molecules, meaning only a small amount of energy is needed to overcome them — they therefore have low melting points.
The correct row shows: non-metals forming covalent bonds + low melting point, which is option C.
✅ Answer: (C)
▶️ Answer/Explanation
Moles of Mg \(= \frac{2.4}{24} = 0.1 \text{ mol}\); moles of \(\text{O}_2\) \(= \frac{5.0}{32} \approx 0.156 \text{ mol}\). The equation requires a 2:1 ratio of Mg to \(\text{O}_2\), so 0.1 mol Mg needs only \(0.05 \text{ mol } \text{O}_2\) — Mg is the limiting reagent and reacts completely, while \(\text{O}_2\) is in excess.
Mass of MgO formed \(= 0.1 \text{ mol} \times 40 \text{ g/mol} = 4.0 \text{ g}\) (alternatively, by conservation of mass: \(2.4 + 1.6 = 4.0\text{ g}\), where 1.6 g of \(\text{O}_2\) is used).
The correct row shows: magnesium reacts completely, mass of MgO = 4.0 g, which is option A.
✅ Answer: (A)
Mass of MgO formed \(= 0.1 \text{ mol} \times 40 \text{ g/mol} = 4.0 \text{ g}\) (alternatively, by conservation of mass: \(2.4 + 1.6 = 4.0\text{ g}\), where 1.6 g of \(\text{O}_2\) is used).
The correct row shows: magnesium reacts completely, mass of MgO = 4.0 g, which is option A.
✅ Answer: (A)
▶️ Answer/Explanation
At the cathode (negative electrode), copper ions \(\text{Cu}^{2+}\) are selectively discharged in preference to hydrogen ions because copper is lower in the reactivity series: \(\text{Cu}^{2+} + 2e^- \rightarrow \text{Cu}\) — copper metal deposits.
At the anode (positive electrode), hydroxide ions from water are discharged in preference to sulfate ions, producing oxygen gas: \(4\text{OH}^- \rightarrow 2\text{H}_2\text{O} + \text{O}_2 + 4e^-\).
The correct row therefore shows: cathode product = copper, anode product = oxygen, which is option C.
✅ Answer: (C)
At the anode (positive electrode), hydroxide ions from water are discharged in preference to sulfate ions, producing oxygen gas: \(4\text{OH}^- \rightarrow 2\text{H}_2\text{O} + \text{O}_2 + 4e^-\).
The correct row therefore shows: cathode product = copper, anode product = oxygen, which is option C.
✅ Answer: (C)
▶️ Answer/Explanation
This reaction involves only bond breaking (the Cl–Cl bond in \(\text{Cl}_2\) is broken to give 2 Cl atoms) with no bond forming — bond breaking always requires energy, making this an endothermic process.
In an endothermic reaction, the products have higher energy than the reactants, so the energy level diagram shows products at a higher level than reactants (energy is absorbed from the surroundings, here supplied by UV light).
This corresponds to diagram D, where the products (\(2\text{Cl}\)) are at a higher energy level than the reactant (\(\text{Cl}_2\)).
✅ Answer: (D)
In an endothermic reaction, the products have higher energy than the reactants, so the energy level diagram shows products at a higher level than reactants (energy is absorbed from the surroundings, here supplied by UV light).
This corresponds to diagram D, where the products (\(2\text{Cl}\)) are at a higher energy level than the reactant (\(\text{Cl}_2\)).
✅ Answer: (D)
▶️ Answer/Explanation
Statements A, B, and C are all correct effects of increasing temperature: particles move faster (greater kinetic energy), collide more frequently, and a larger proportion exceed the activation energy threshold.
Activation energy is a fixed energy barrier for a specific reaction — it is a property of the reaction itself and is not lowered by increasing temperature (catalysts lower activation energy, not temperature).
Therefore, statement D is incorrect — activation energy does not decrease at higher temperatures.
✅ Answer: (D)
Activation energy is a fixed energy barrier for a specific reaction — it is a property of the reaction itself and is not lowered by increasing temperature (catalysts lower activation energy, not temperature).
Therefore, statement D is incorrect — activation energy does not decrease at higher temperatures.
✅ Answer: (D)
▶️ Answer/Explanation
Oxidation is loss of electrons (OIL — Oxidation Is Loss). Bromide ions \(\text{Br}^-\) (oxidation state \(-1\)) are converted to bromine \(\text{Br}_2\) (oxidation state \(0\)) — they lose electrons and are therefore oxidised: \(2\text{Br}^- \rightarrow \text{Br}_2 + 2e^-\).
Simultaneously, sulfur in \(\text{H}_2\text{SO}_4\) (oxidation state \(+6\)) is reduced to \(\text{SO}_2\) (oxidation state \(+4\)) by gaining electrons — this is the reduction half-reaction.
Sodium and hydrogen ions do not change oxidation state in this reaction, so they are neither oxidised nor reduced.
✅ Answer: (B)
Simultaneously, sulfur in \(\text{H}_2\text{SO}_4\) (oxidation state \(+6\)) is reduced to \(\text{SO}_2\) (oxidation state \(+4\)) by gaining electrons — this is the reduction half-reaction.
Sodium and hydrogen ions do not change oxidation state in this reaction, so they are neither oxidised nor reduced.
✅ Answer: (B)
▶️ Answer/Explanation
Ammonia (\(\text{NH}_3\)) is the only common gas that is alkaline; when it dissolves in the water on damp red litmus paper, it forms ammonium hydroxide solution, turning the paper blue.
A lighted splint tests for hydrogen (squeaky pop) or oxygen (relights the splint); limewater tests for carbon dioxide (turns milky); sodium hydroxide solution is used to test for metal ions in solution, not gases.
Damp red litmus paper turning blue is the unique and definitive test for ammonia gas.
✅ Answer: (C)
A lighted splint tests for hydrogen (squeaky pop) or oxygen (relights the splint); limewater tests for carbon dioxide (turns milky); sodium hydroxide solution is used to test for metal ions in solution, not gases.
Damp red litmus paper turning blue is the unique and definitive test for ammonia gas.
✅ Answer: (C)
▶️ Answer/Explanation
Group I elements (lithium, sodium, potassium, etc.) are metals — they have a metallic lustre and conduct electricity — eliminating options C and D which describe non-metals and gases.
Unlike most metals, Group I elements are unusually soft: sodium and potassium can be cut with a knife, revealing a shiny surface. They also have low melting points relative to other metals.
They are also highly reactive (not unreactive), reacting vigorously with water and air.
✅ Answer: (B)
Unlike most metals, Group I elements are unusually soft: sodium and potassium can be cut with a knife, revealing a shiny surface. They also have low melting points relative to other metals.
They are also highly reactive (not unreactive), reacting vigorously with water and air.
✅ Answer: (B)
▶️ Answer/Explanation
Statement 1 is wrong: transition elements are dense metals (e.g. iron, copper, nickel) and they sink in water — only Group I metals like lithium float on water due to their very low density.
Statement 2 is not necessarily correct: transition metal oxides are often coloured (e.g. \(\text{CuO}\) is black, \(\text{Fe}_2\text{O}_3\) is red-brown); white oxides are more characteristic of Group II metals.
Statement 3 must be correct: all transition metal oxides are basic (they react with dilute acids to form a salt and water), which is a defining property of metal oxides.
✅ Answer: (D)
Statement 2 is not necessarily correct: transition metal oxides are often coloured (e.g. \(\text{CuO}\) is black, \(\text{Fe}_2\text{O}_3\) is red-brown); white oxides are more characteristic of Group II metals.
Statement 3 must be correct: all transition metal oxides are basic (they react with dilute acids to form a salt and water), which is a defining property of metal oxides.
✅ Answer: (D)
▶️ Answer/Explanation
From the displacement reactions: Q displaces X (so Q > X in reactivity); X displaces T (so X > T); T displaces Z (so T > Z). The reactivity order is therefore Q > X > T > Z.
The most reactive metal has the greatest tendency to lose electrons and form positive ions — this is a fundamental principle of the reactivity series.
Since Q is the most reactive, Q has the greatest tendency to form positive ions.
✅ Answer: (A)
The most reactive metal has the greatest tendency to lose electrons and form positive ions — this is a fundamental principle of the reactivity series.
Since Q is the most reactive, Q has the greatest tendency to form positive ions.
✅ Answer: (A)
▶️ Answer/Explanation
Filtration passes water through beds of sand and gravel to physically remove suspended solid particles, making the water clear — it does not kill bacteria.
Chlorination involves adding small, carefully controlled amounts of chlorine to kill bacteria and other harmful microorganisms, making water safe for drinking.
The correct row shows: filtration → removes solids/particles; chlorination → kills microorganisms/bacteria, which corresponds to option D.
✅ Answer: (D)
Chlorination involves adding small, carefully controlled amounts of chlorine to kill bacteria and other harmful microorganisms, making water safe for drinking.
The correct row shows: filtration → removes solids/particles; chlorination → kills microorganisms/bacteria, which corresponds to option D.
✅ Answer: (D)
▶️ Answer/Explanation
The Contact process has four key steps; only one is reversible: \(2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g)\) — this is the conversion of sulfur dioxide to sulfur trioxide using a vanadium(V) oxide catalyst at 450 °C.
The other steps — burning sulfur, absorbing \(\text{SO}_3\) into \(\text{H}_2\text{SO}_4\) to form oleum, and diluting oleum — are all essentially irreversible.
The reversible nature of step B is why industrial conditions (temperature and pressure) must be carefully optimised to maximise yield.
✅ Answer: (B)
The other steps — burning sulfur, absorbing \(\text{SO}_3\) into \(\text{H}_2\text{SO}_4\) to form oleum, and diluting oleum — are all essentially irreversible.
The reversible nature of step B is why industrial conditions (temperature and pressure) must be carefully optimised to maximise yield.
✅ Answer: (B)
▶️ Answer/Explanation
The structure shown contains a carbon-carbon double bond (\(\text{C=C}\)), indicating it is an alkene; the chain length and position of the double bond determine the full IUPAC name.
In IUPAC nomenclature, the chain is numbered from the end closest to the double bond, and the position number of the first carbon of the double bond is stated (e.g. but-1-ene, but-2-ene).
The structure corresponds to option B based on the number of carbons and position of the double bond shown in the diagram.
✅ Answer: (B)
In IUPAC nomenclature, the chain is numbered from the end closest to the double bond, and the position number of the first carbon of the double bond is stated (e.g. but-1-ene, but-2-ene).
The structure corresponds to option B based on the number of carbons and position of the double bond shown in the diagram.
✅ Answer: (B)
▶️ Answer/Explanation
Both springs start at the same length when load = 0, so their unstretched lengths are equal — eliminating option B. Both show linear sections, so both obey Hooke’s law up to their respective limits — eliminating option A.
The graph shows Y’s line curves (reaches its limit) at a higher load than X, meaning Y needs a greater load to reach its limit of proportionality — this makes option D correct.
Regarding spring constant: spring X has a steeper gradient (more extension per unit load) — actually X is less stiff, with a smaller \(k\), so option C is also incorrect.
✅ Answer: (D)
The graph shows Y’s line curves (reaches its limit) at a higher load than X, meaning Y needs a greater load to reach its limit of proportionality — this makes option D correct.
Regarding spring constant: spring X has a steeper gradient (more extension per unit load) — actually X is less stiff, with a smaller \(k\), so option C is also incorrect.
✅ Answer: (D)
▶️ Answer/Explanation
Using the formula \(E = P \times t\), first convert time to seconds: \(2.0 \text{ min} = 2.0 \times 60 = 120 \text{ s}\).
Then: \(E = 900 \text{ W} \times 120 \text{ s} = 108\,000 \text{ J} = 108 \text{ kJ}\).
A common error is forgetting to convert minutes to seconds — using 2 minutes directly gives 1800 J, which is not one of the options.
✅ Answer: (D)
Then: \(E = 900 \text{ W} \times 120 \text{ s} = 108\,000 \text{ J} = 108 \text{ kJ}\).
A common error is forgetting to convert minutes to seconds — using 2 minutes directly gives 1800 J, which is not one of the options.
✅ Answer: (D)
▶️ Answer/Explanation
Non-renewable sources are those that will eventually run out and cannot be replenished in a human lifetime: coal, natural gas, oil, and nuclear fission (uranium fuel) all fall into this category.
Geothermal, solar, and wind are all renewable — they are continuously replenished by natural processes (Earth’s heat, sunlight, and wind will not run out on a human timescale).
Only option A (coal, gas, nuclear fission) contains exclusively non-renewable sources.
✅ Answer: (A)
Geothermal, solar, and wind are all renewable — they are continuously replenished by natural processes (Earth’s heat, sunlight, and wind will not run out on a human timescale).
Only option A (coal, gas, nuclear fission) contains exclusively non-renewable sources.
✅ Answer: (A)
▶️ Answer/Explanation
Evaporation occurs at the surface of a liquid at any temperature, when the most energetic molecules have enough kinetic energy to overcome intermolecular forces and escape into the gas phase.
As the highest-energy molecules leave, the average kinetic energy of the remaining molecules decreases — this is why the liquid cools.
This distinguishes evaporation from boiling, which occurs throughout the liquid at a fixed boiling point; condensing is the reverse (gas → liquid); melting is solid → liquid.
✅ Answer: (C)
As the highest-energy molecules leave, the average kinetic energy of the remaining molecules decreases — this is why the liquid cools.
This distinguishes evaporation from boiling, which occurs throughout the liquid at a fixed boiling point; condensing is the reverse (gas → liquid); melting is solid → liquid.
✅ Answer: (C)
▶️ Answer/Explanation
In solids, particles are tightly packed with strong intermolecular forces and only vibrate — they expand the least when heated. In liquids, particles are close but can move — they expand more than solids but less than gases.
In gases, particles are far apart and move freely with very weak intermolecular forces — they expand the most when heated (gases can expand to fill any container).
The order from smallest to largest expansion is: solid → liquid → gas, which is option D.
✅ Answer: (D)
In gases, particles are far apart and move freely with very weak intermolecular forces — they expand the most when heated (gases can expand to fill any container).
The order from smallest to largest expansion is: solid → liquid → gas, which is option D.
✅ Answer: (D)
▶️ Answer/Explanation
A plane (flat) mirror forms an image that is: virtual (behind the mirror), upright (not inverted), the same size as the object, and at the same distance behind the mirror as the object is in front.
Therefore, option A is correct — the image distance equals the object distance from the mirror surface.
Options B and C are wrong (same size, not diminished or enlarged); option D is wrong (the image is upright, not inverted vertically, though it is laterally reversed left-to-right).
✅ Answer: (A)
Therefore, option A is correct — the image distance equals the object distance from the mirror surface.
Options B and C are wrong (same size, not diminished or enlarged); option D is wrong (the image is upright, not inverted vertically, though it is laterally reversed left-to-right).
✅ Answer: (A)
▶️ Answer/Explanation
The refractive index is defined as \(n = \dfrac{c}{v}\), where \(c\) is the speed of light in a vacuum (\(3 \times 10^8 \text{ m/s}\)) and \(v\) is the speed of light in the medium — this is always \(\geq 1\) since light slows down in any medium.
Frequency is not affected by refraction — only speed and wavelength change — so options C and D involving frequency are incorrect.
Option A correctly places the vacuum speed in the numerator and the substance speed in the denominator, giving \(n \geq 1\) for all optical media.
✅ Answer: (A)
Frequency is not affected by refraction — only speed and wavelength change — so options C and D involving frequency are incorrect.
Option A correctly places the vacuum speed in the numerator and the substance speed in the denominator, giving \(n \geq 1\) for all optical media.
✅ Answer: (A)
▶️ Answer/Explanation
The electromagnetic spectrum in order of increasing wavelength is: gamma → X-rays → UV → visible → infrared → microwaves → radio waves.
From the three given: X-rays have the shortest wavelength (around \(10^{-10}\) m), infrared is intermediate (around \(10^{-5}\) m), and radio waves have the longest wavelength (up to several metres or kilometres).
The correct order from smallest to largest wavelength is: X-rays → infrared → radio waves, which is option C.
✅ Answer: (C)
From the three given: X-rays have the shortest wavelength (around \(10^{-10}\) m), infrared is intermediate (around \(10^{-5}\) m), and radio waves have the longest wavelength (up to several metres or kilometres).
The correct order from smallest to largest wavelength is: X-rays → infrared → radio waves, which is option C.
✅ Answer: (C)
▶️ Answer/Explanation
Resistance is proportional to length \(l\) and inversely proportional to cross-sectional area \(A\): \(R \propto \frac{l}{A}\). Since \(A \propto d^2\), a smaller diameter means smaller area and therefore higher resistance.
To increase resistance: increasing \(l\) increases \(R\), and decreasing \(d\) decreases \(A\), which also increases \(R\) — both changes work in the same direction.
Option C (increasing \(l\) and decreasing \(d\)) therefore guarantees an increase in resistance; all other options have at least one change that would decrease resistance.
✅ Answer: (C)
To increase resistance: increasing \(l\) increases \(R\), and decreasing \(d\) decreases \(A\), which also increases \(R\) — both changes work in the same direction.
Option C (increasing \(l\) and decreasing \(d\)) therefore guarantees an increase in resistance; all other options have at least one change that would decrease resistance.
✅ Answer: (C)
▶️ Answer/Explanation
An NTC thermistor has decreasing resistance as temperature increases — this is its defining characteristic (Negative Temperature Coefficient).
As thermistor resistance decreases, the total circuit resistance decreases, so the total current increases. The voltage across the fixed resistor \(V = IR\) increases because more current flows through it.
The voltmeter reading (across the resistor) therefore increases. This corresponds to option B: thermistor resistance decreases, voltmeter reading increases.
✅ Answer: (B)
As thermistor resistance decreases, the total circuit resistance decreases, so the total current increases. The voltage across the fixed resistor \(V = IR\) increases because more current flows through it.
The voltmeter reading (across the resistor) therefore increases. This corresponds to option B: thermistor resistance decreases, voltmeter reading increases.
✅ Answer: (B)
▶️ Answer/Explanation
A fuse must have a current rating just above the normal operating current of the appliance — it should blow if there is a fault (excess current) but not blow during normal use.
The correct fuse is the smallest available rating that is still greater than the normal operating current: for example, an appliance drawing 2 A should use a 3 A fuse (not 5 A or 13 A, which would be too slow to blow in a fault).
Option B shows the appliance-fuse combination where the fuse rating is the lowest available rating that still exceeds the normal current — this is the most appropriate choice.
✅ Answer: (B)
The correct fuse is the smallest available rating that is still greater than the normal operating current: for example, an appliance drawing 2 A should use a 3 A fuse (not 5 A or 13 A, which would be too slow to blow in a fault).
Option B shows the appliance-fuse combination where the fuse rating is the lowest available rating that still exceeds the normal current — this is the most appropriate choice.
✅ Answer: (B)
▶️ Answer/Explanation
By Faraday’s law, the induced e.m.f. is proportional to the rate of change of magnetic flux. Moving the magnet more slowly reduces the rate of flux change, which decreases the induced e.m.f.
Adding more turns increases the e.m.f. (more flux linkage); moving faster increases it; turning the magnet around reverses the direction but does not reduce the magnitude.
Only option C (moving more slowly) directly reduces the magnitude of the induced e.m.f.
✅ Answer: (C)
Adding more turns increases the e.m.f. (more flux linkage); moving faster increases it; turning the magnet around reverses the direction but does not reduce the magnitude.
Only option C (moving more slowly) directly reduces the magnitude of the induced e.m.f.
✅ Answer: (C)
▶️ Answer/Explanation
In beta-minus (\(\beta^-\)) decay, a neutron in the nucleus decays into a proton and an electron (the \(\beta^-\) particle is emitted): the mass number stays the same (still 14) and the atomic number increases by 1 (from 6 to 7).
The nuclear equation is: \(_{6}^{14}\text{C} \rightarrow _{7}^{14}\text{N} + _{-1}^{0}e\). The product has mass number 14 and atomic number 7, which is nitrogen-14.
This corresponds to option C: \(_{7}^{14}\text{N}\).
✅ Answer: (C)
The nuclear equation is: \(_{6}^{14}\text{C} \rightarrow _{7}^{14}\text{N} + _{-1}^{0}e\). The product has mass number 14 and atomic number 7, which is nitrogen-14.
This corresponds to option C: \(_{7}^{14}\text{N}\).
✅ Answer: (C)