MPTET Varg 2 Science Mock Test - 4 - MPTET MCQ

The correct answer is 31 pairs.

Key Points

Spinal nerves: it is a part of the peripheral nervous system.

• Spinal nerves are the path of communication between the spinal cord and the specific region of the body.
• these nerves leave the vertebral column by passing through the intervertebral foramina except the first spinal nerve which emerges b/w the occipital bone and atlas (first vertebra).

Explanation:-

• There are 31 pairs of spinal nerves that originate from both sides of the spinal cord.

Science is a kind of subject that just depends on the understanding and construction of knowledge. Any student belonging to any gender or any community can construct his knowledge in science if he has a proper understanding and interest to learn science. Other than this there are no other conditions for a student to learn and understand science in a better way like belonging to a particular community etc. 
Key Points

• Assertion A  gender players and important role in achievement in science is totally wrong because there is no relation between achievement in science and gender people belonging to any gender can achieve a lot in science if they are interested and skilled enough to understand the concepts clearly and experiment according to it. Finally arrive at the conclusion and assess it.
• Reasoning R the information processing strategies are different for boys and girls is also wrong because the curriculum and syllabus of science are equal for every student in the class and also the information processing for the teaching strategies are also same and our design according to the cognitive abilities and learning difficulties of the students but not according to the gender or any other means.

Hence Both (A) and (R) are incorrect.

Explanation-

An oxidizing agent is a substance that causes oxidation by accepting electrons; therefore, it gets reduced.

A reducing agent is a substance that causes reduction by losing electrons; therefore it gets oxidized.

Given data and Analysis-

Cr2O72-(aq) + SO32-(aq) → Cr3 + (aq) + SO42-(aq)

In the above reaction, in Cr₂O₇, Cr is in a +6 oxidation state which gets converted to a +3 oxidation state. So it can not be reduced further.

In SO₃²-, S is in a +4 oxidation state. It acted as a reducing agent so statement 3 is incorrect.

In SO₄^2- S is in a +6 oxidation state.

Sulfate is a very weak oxidizing agent. Since sulfur is in its maximum oxidation number in sulfate ion, this ion cannot act as a reducing agent. So statement 1 is correct.

CONCEPT:

• Work-energy theorem: It states that the sum of work done by all the forces acting on a body is equal to the change in the kinetic energy of the body i.e.,

Work done by all the forces = Kf - Ki

Where v = final velocity, u = initial velocity and m = mass of the body

EXPLANATION:

Given that:

• Mass of the Object (m) = 1 kg
• Initial velocity of the object (u) = 4m/s
• Final velocity of the object (v) = 8m/s
• Total net work is done W _(net) = Kinetic energy (During final velocity) – Kinetic Energy (During Initial Velocity).
• Now by substituting the values in the above equation, we get

W_(net) = ½ mv² – ½ mu²

= ½ (1)×(8)² – ½ (1)×(4)²

= 32 - 8 Joule

= 24 Joules.

• Therefore, the total work done by the force is 24 J.

Concept:

• Sodium hydrogen carbonate (NaHCO3) commonly known as Baking Soda is prepared when Sodium Chloride is reacted with water along with Ammonia (NH3) and carbon dioxide.
• It can be given as in the form of the equation as

NaCl + H2O + CO2 + NH3 ⇒ NaHCO3 + NH4Cl

• Where NH4Cl is ammonium chloride.
• Baking Soda is widely used for cooking etc.
• When Baking Soda is mixed with a mild acid like tartaric acid in presence of water or carbon dioxide we get Baking Powder.
• Its Chemical equation can be given as NaHCO3 + H+ ⇒ H2O + CO2 + Sodium Acid Salt

Explanation:

• The reaction of Baking Soda with water produces water, carbon dioxide and Sodium carbonate.
• The baking soda solution is a basic solution and has a pH > 7.
• The solution thus becomes basic in nature.
• Phenolphthalein is an indicator and changes its colour when a solution is alkaline to pink.
• Phenolphthalein is colourless in acidic solution.

Thus when phenolphthalein is added to baking soda, it will turn pink.

Additional Information

•  Some indicators and their colour change are given in the table below:

Concept:

Frictional Force

• The resistive force offered by one surface over the other surface, when one slides over the other is known as frictional force.
• It prevents the relative motion between two surfaces.
• The Frictional force can be both desirable and undesirable depending upon the requirement. 
• It is a contact force. 
• ​The different types of Frictional Forces are Rolling Friction, Sliding Friction, and Static Friction. 
• The cause of frictional force is interlocking between surfaces at the molecular level.

Types of Friction

• Sliding Friction: The frictional force acting between surfaces when one of them is sliding on another is sliding friction. 
• Rolling Friction: When one body rolls over the surface of another body, the resistance to its motion is called rolling friction. 
• Static Friction: The frictional force which is acted when the object is kept stationary on the surface. 

Explanation:

• Rolling friction is having the least value. 
• This is evident from the fact, that it is easier to roll an object on wheels rather than sliding it. 
• Static friction has the highest value. This can be observed as the object is kept at rest. 

So, the correct sequence is Rolling Friction < Sliding Friction < Static Friction

Important Points

•  While rolling the point of contact between surface keep on changing. The frictional force being the contact force gets reduced. 
• So, the rolling friction has the least value. 
• Thats why wheels are used to carry objects. 

Key Points

• Haemophilia is a genetic disorder that can be inherited from one generation to the next.
• It is classified as a Mendelian disorder which is caused by a mutation in a single gene.
• It is a sex-linked recessive disorder i.e., the inheritance of this disorder is associated with the sex chromosomes.
• In a recessive disorder, the disease is expressed only in homozygous recessive state i.e., when 2 recessive alleles for the trait are present in an individual.
• In a sex-linked recessive disorder:
  • Normal - Woman with XX; Man with XY.
  • Affected - Woman with X^hX^h; Man with X^hY. [X^h is the affected allele]
  • Carrier - Woman with X^hX chromosomes.
• If a woman has heterozygous condition, she becomes a carrier for the disease.
• A carrier does not express the disease but can transfer the disease to the next generation.

Explanation:

• Queen Victoria was a carrier of haemophilia and therefore, passed on the disease to several descendants.
• This is why haemophilia is also known as 'the royal disease'.
  • Hence, option (2) is correct.
• The mutation affects a single protein involved in the blood clotting process.
• This results in non-stop bleeding even in case of a small cut or wound.
  • Hence, option (3) is correct.

Additional Information

Features of sex-linked (X-linked) recessive disorder:

• Males can pass on the disease only to a daughter.
• Females can pass the disease to son and daughter both.

Concept:

Oxidation:

It is the process in which an atom, molecule, or ion loses one or more electrons.

Reduction:

It is the process in which an atom, molecule, or ion gains one or more electrons.

Reducing agent/ Reductant:

• It is one that donates electrons to a species and thereby brings about its reduction.
• The reducing agent is oxidized by having its electrons taken away.
• Eg: In the reaction , the oxidizing agent is MnO2 and the reducing agent is HCl.

Oxidizing agent/ Oxidizer:

• It is defined as a substance that removes electrons from another reactant in a redox chemical reaction.
• The oxidizing agent is reduced by taking electrons onto itself.
• In the reaction , the oxidizing agent is O2 and the reducing agent is Mg.

Explanation:

• As the electronegativity of a species increases, its tendency to pull electrons also increases and eventually behaves as a stronger oxidizing agent.
• Greater the reduction potential, greater will be the tendency of oxidizing agent to get reduced easily and hence acts as a stronger oxidizing agent.

H₂O₂:

• Hydrogen peroxide acts as an oxidizing agent and reducing agent.
• Eg: of reaction in which H₂O₂ acts as an oxidizing agent is as follows: 

O₃:

• Ozone is a strong oxidizing agent.
• It can easily lose nascent oxygen.
• An example of a reaction in which O₃ acting as an oxidizing agent is: 

K₂Cr₂O₇:

• It acts as an oxidizing agent in an acidic medium and can oxidize reducing agents like ferrous sulfate, nitrite, sulfite, etc.
• In these reactions in acid solution, dichromate is reduced to green Cr³⁺ ions: 

KMnO₄:​

• It dissolves in water to give an intensely purple solution.
• KMnO₄ is stronger than any other oxidizing agent because it contains Mn in its highest oxidation state +7.
• Elements become more electronegative as the oxidation state of their atoms is increased.
• Their reaction is as follows: 

The increasing order of reduction potential of the given oxidizing agent is: 

Hence, the increasing order of power of the oxidizing agent is : 

Therefore, ozone is the strongest oxidizing agent.

Correct Answer: b) Iron
Galvanization is a process in which a protective zinc coating is applied to iron or steel to prevent rusting.

Concept:

Biodegradable wastes:

• The wastes that can be degraded or decomposed in nature by the action of different microbes and other living things using processes like composting, aerobic digestion, anaerobic digestion, etc are called Biodegradable wastes.
• Examples include wood, fruits, vegetables, dead animal and plants, etc.
• These wastes majorly include organic matter which can be broken down into simpler organic molecules like carbon dioxide, methane, water.
• However, some Inorganic matters are also included which can be degraded by microbial action like gypsum.

​Non-biodegradable wastes:

• The wastes that cannot be degraded or decomposed in nature by the action of different microbes and other living things using processes like composting, aerobic digestion, anaerobic digestion, etc are called Non-Biodegradable wastes.
• These wastes act as a source of environmental pollution.
• Examples include plastic, glass, metallic wastes, etc.​

​​​​​​

​Explanation:

• Wood, spoilt food, and vegetable peels all come under the category of organic matter which can be easily degraded by microbial action.
• These things act as natural manure after decomposition and can be used to increase soil fertility.

Additional Information

•  Bubble wraps, PVC pipes, Bakelite switches, Empty milk sachets, Plastic cans, and DDT all are Non-biodegradable wastes as they are not decomposed in nature.

Concept-:

• The total number of electrons (or protons) in a neutral atom is called its atomic number, denoted by Z.
• The total number of protons and neutrons in the nucleus of an atom is known as its Mass Number and is denoted by A. 
• The number of neutrons is calculated by the difference in M-A.
• An element is represented as writing the symbol and writing the atomic number as subscript and atomic mass as superscript like _ZX^A.
• When an element gains one electron, the number of electrons exceed the number of protons ang hence it gains negative charge,
• The negative charge is equal to the number of electrons gained.
• When an element loses electrons, it gains a positive charge and the amount of positive charge is equal to the number of loss in protons.
• The negatively charged species is called the anion is written as X^- whereas the positively charged species is called the cation.

​Calculation:

​Given:

• Mass number of X = 37.

Hence, the number of protons + neutrons = 37.

To maintain electrical neutrality, we know the number of electrons must be equal to the number of protons.

Hence, the number of electrons + neutrons in neutral atom = 37.

When the atom gains one electron, the sum becomes 38.

Hence, total number of electrons + neutrons in anion X = 38.

Now, it is given that the anion contains 11. 2% more neutrons than electrons. 

Let the number of electrons be x. So, the number of neutrons will be x + 11.2 % of x = x +.112x.

Hence, total number of electrons + neutrons in anion X =

 x +.112x + x = 38

or, 2.112x = 38

or, x = 17.99 = 18.

Anion have 18 electrons so the number of proton or atomic number will be 17

Hence, the symbol of the anion will be: ₁₇³⁷X^-

Concept:

Allylic halogenation:

• When alkenes are subjected to halogenation under high temperatures, allylic halogenation takes place.
• The reaction takes place via a free radical mechanism.
• The substitution reaction takes place at higher temperatures and not an addition reaction.

Explanation:

Let us study the mechanism of the reaction.

• In the first step, bromine dissociates homolytically giving two free radicals as shown below.

• The second step is the chain propagation step where Bromine free radical takes up hydrogen radical.
• Allylic free-radical intermediate is formed which is resonance stabilized.
• A combination of allylic free radical takes place with the bromine free radical giving us product A.

• The last step is the combination of free radicals to stop the chain reaction.

Hence, in the reaction ​​ the product formed is .

Important Points

• Formation of CH3-CH=CHBr and  product does not take place because it would require a less stable radical intermediate.

Mistake Point

• Alkenes undergo an addition reaction with Br₂ in organic solvents and the products are dihalides.

The correct answer is All of the above.

Key Points

• Mendel worked in the garden and formulated laws.
• Mendel proposed the law of dominance, the law of segregation, and the law of independent assortment.
• The Law of dominance states that characters are controlled by factors, and these factors are now called genes.
• Factors occur in pairs,  for example, genes for tall height will have Tt and TT.
• In a pair of factors, one dominates, and the other is recessive.
• In a genotype Tt, T is dominant, and t is recessive.

Additional Information 

Punnet square depicts the dominant interaction

The correct answer is Negative.

Key Points

• Negative work done means that force is opposite to displacement.
• Two objects that are of like charge will repel each other.
  • That is, a positively charged object will exert a repulsive force upon a second positively charged object.
  • This repulsive force will push the two objects apart.
  • Hence, the work done is negative.

Additional Information

• Positive work done means that force is parallel to displacement.
  • Example: when a body falls freely under gravitational pull.
• If the force is perpendicular to the displacement and if either the force or the displacement is zero, the work done will be zero.
  • Example: when a body is moved along a circular path.

Concept: 

• Antibiotics are substances released from some microorganisms which are harmful to other organisms.
• Antibiotics are widely used in the treatment of infections.
• Antibiotics can kill the infecting organism or can restrict its growth.
• The first antibiotic was discovered by Alexander Fleming and it was penicillin.

Explanation:

Option 1: viruses show metabolism of their own – INCORRECT

• Metabolism is the characteristic feature of living beings while viruses use host machinery for replication and survival.
• Hence, this option is incorrect.

Option 2: viruses are too small in size for antibiotics to act upon them – INCORRECT

• Antibiotics act on the parts of the cell not on the whole cell and that's why the size of the cell can not affect the action of antibiotics.
• Hence, this option is incorrect.

Option 3: viruses show no metabolism of their own – CORRECT

• Viruses do have cellular organization, they also lack the enzymes that are essential for the synthesis of proteins and nucleic acids. 
• Viruses don’t have cell walls and show no metabolic processes.
• But once they enter the host, they set up cellular metabolism and start to make a replica of themselves by using the host machinery, in the host body.
• Hence, this option is correct.

Option 4: viruses produce a thick covering and encyst themselves as endospores – INCORRECT

• Endospore is a characteristic feature of bacteria.
• Hence, this option is incorrect.

So, the correct answer is Option 3: viruses show no metabolism of their own.

The competency-based teaching method permits students to boost based on their capacity to master a talent or competency at their very own pace no matter their surroundings. This approach is suitable to meet different learning abilities and can lead to more efficient student outcomes.

Important Points

Some of the primary characteristics of competency-based education are :

• Students learn at their very own pace
• Flexibility
• Personalized manner of teaching
• Timely aid
• Purpose-pushed
• A novelty in the evaluation and grading
• A specific strategy for communicating progress
• A talent-based education application that ensures quality
• Affordability
• Peer assistance

Therefore, alternative (a), the students practicing the multiplication table chart isn't suitable right here.

Additional Information

The usefulness of Competency-Based Approach:

• The competency-based approach keeps the learner away from rote memorization.
• What the students learn today cannot be forgotten tomorrow as competencies are achieved by the students at the level of mastery under your guidance.
• The assessments of competencies are directly linked with the objectives of the learning experience and are expected to be continuous and competence-based.
• The assessment results can be used for further improvement of the students.
• Remedial coaching is helpful for the low achievers and enrichment program for the high achievers. Since it aims at mastery of skills by each individual it caters to the learning needs of all categories of students.
• Suitable activities like storytelling, role-playing, dialogue, practice riddle, wordplay, magic, quiz, and puzzle help the students to achieve the competencies in learner-friendly ways.
• The teaching-learning process is joyful and interesting in this approach.

 Concept :

 Conditions required for the formation of shadow :

• There should be an opaque object.
• There should be a source of light.
• The object must be placed in the path of light.
• The shadow should be formed on a screen.

Explanation :

• A Blackboard is an opaque object.
• Opaque objects completely block the passage of light coming from the source.
• When lights fall on a blackboard, a shadow is formed.

So, the correct answer is Both Assertion and Reason are true but the reason is not the correct explanation of Assertion.

Additional Information

• Some examples of opaque objects are wood, stone, and ceramics.
• Mirror reflection gives us clear images.
• Images are very different from shadows.

The correct answer is Spleen.

Key Points

• Spleen
  • ​The spleen is the largest organ of the lymphatic system.
  • It keeps all the body fluids balanced.
  • It is made up of red pulp tissue that filters the old and damaged red blood cells, whereas, the white pulp tissue consists of the B and T cells that help to fight infections.
  • The spleen is a bean-shaped organ that stores erythrocytes, lymphocytes, and phagocytes.
  • The spleen recycles the old and damaged red blood cells and the white blood cells are stored.
  • It also helps to fight against bacteria that cause diseases such as meningitis and pneumonia.

Additional Information

• Tonsil
  • Tonsils are the two lymph nodes located on each side of the back of your throat.
  • They function as a defence mechanism and help prevent your body from getting an infection.
  • When it becomes infected, the condition is called tonsilitis.
• Thymus
  • The thymus gland is a very unique organ that is at its largest in children and shrinks away as the body grows older.
  • It is about 2.5 to 5 cm wide, 4 to 6 cm long, and 1cm thick at birth.
• Lymph node
  • A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system, and the adaptive immune system.
  • A large number of lymph nodes are linked throughout the body by the lymphatic vessels.

Concept: 

• Bacteria can be categorized into 4 different types based on the number of flagellum present.
• Monotrichous, Amphitricous, Peritrichous & Lophotrichous

​

​Explanation:

• Vibrio cholerae is a Monotrichous bacteria. It only has a single flagellum present on the pole
• Vibrio cholerae is a Gram-negative, comma-shaped bacterium. The bacterium's natural habitat is brackish or saltwater where they attach themselves easily to the chitin-containing shells of crabs, shrimps, and other shellfish.
• It causes the disease cholera

Important Points

• The flagellum is mainly divided into three parts:

      1. Filament: It lies external to the cell surface

      2. Hook: It is embedded or fit in the cell envelope.

      3. Basal body:  It is composed of a central rod inserted into a series of rings which is attached to the cytoplasmic membrane and cell wall.

Additional Information 

• Amphitrichous – Single flagellum present on both sides. Eg - Alkaligens faecalis
• Peritrichous – Entire body of the bacteria is covered with flagella. Eg –  Salmonella Typhi
• Lophotricous – Tuft (bunch) of flagella present on one or both sides. Eg – Spirillum.

The correct answer is 3 ​Ω.

Key Points

• Resistors in Parallel: 
  • Both of a resistor's terminals are linked to the respective terminals of another resistor or resistor.
  • In this, the circuit current can take more than one path as there are multiple paths for the current.
  • The current may not be the same in the parallel network.
  • It has a common voltage across the network.

​CALCULATION:

• The reciprocal of the equivalent resistance (R_p) of a group of resistances joined in parallel is equal to the sum of the
  reciprocals of the individual resistances that is 
  • ​1/Rp = 1/R₁ + 1/R₂ + 1/R₃ + ......1/R_n  

                            = 1/12 + 1/12 + 1/12 + 1/12 

                            = 4/12 = 1/3 

                       R_p = 3 Ω

Hence, the total equivalent resistance of the circuit is 3 Ω.

Additional Information

• Conductance:
  • It is the reciprocal or the inverse of resistance.
  • It is symbolized by G ( G = 1/R ).
  • Its unit is called Siemens, represented by the symbol S.
  • To convert it back into resistance we take the reciprocal of it.

NCF-2005 refers to the National Curriculum Framework published in 2005, by the NCERT. It is the official document which states that the curriculum must be student-centric and beyond the textbooks.

Key Points

Recommendation of NCF regarding Science curriculum at the upper primary stage:

• The scientific concepts to be taught at this stage should be chosen to make sense of everyday experiences as to make the students familiar with the use and application of scientific knowledge in their real life.
• It should focus on developing the cognitive (related to the mental processes), affective (related to the development of emotions of students), and psychomotor domains (related to the development of motor skills).
• It also recommended that the science curriculum should be student-centered i.e., all the teaching-learning activities conducted in science teaching should be in accordance with the needs, desires, and interests of the students.
• The curriculum of science should be inquiry-based to make the students independent discoverers of knowledge that will help them to apply the scientific knowledge into their real life.
• Science education should create opportunities for students to perform research and experiments on their own to explore, discuss, and debate environmental issues, problems of health, etc. so that they can get hands-on experiences that will enhance their conceptual learning of science.
• For example, they can conduct experiments to know the presence of chlorophyll in the leaves of plants and trees. 
• Science should be a core compulsory subject up to Class X as the learned concepts of science will help the students to solve their problems in the real world.

Hint

• Teacher-centered curriculum refers to the active involvement of the teacher in the teaching-learning process while the learners passively listen to the teacher. 

So, it is concluded that NCF recommends a teacher-centered science curriculum, is not a key recommendation as per NCF on the science curriculum

Science (from the Latin word Scientia, meaning knowledge ) is the activity and application of knowledge and understanding of the social and natural world around us followed by a systematic approach based on evidence.

Technology is the application of scientific knowledge for practical purposes. To achieve goals, skills methods, and processes used is technology.

Key Points

• Science includes the study of the physical and biological world around us through several approaches like observation, experimenting, inference, etc while technology involves the application of that scientific knowledge for practical purposes.
• Science and technology both are creative in their own way.
• Science and technology both are present from ancient times.
• Science and technology are not the same but they do have an impact on each other.
• Science and technology are different but related and interdependent fields.

Important Points

Difference between science and technology

Conclusion: Science is broad or divergent while technology is goal-oriented.

The Correct Answer is Option 3 i.e Double displacement reaction.

• Displacement reaction:
  • In these reactions, an atom/ion present in a compound gets replaced by an atom/ion of another element.
  • Example: FeSO₄ + Zn → ZnSO₄ + Fe
• Decomposition reaction:
  • In these reactions, compound either of its own or upon heating decomposes to given two or more components out of which at least one is in the elemental state. 
  • Example: 2NaH → Na + H_2​
• Double displacement reaction:
  • In these reactions, two compounds exchange ions to form two new compounds.
  • Example: Na₂S + 2HCL → 2NaCl + H₂S
• Double decomposition reaction:
  • It is a chemical reaction in which the ions of two compounds mutually exchange their places to form two new compounds.
  • CuSO₄ + H₂S → CuS + H₂SO₄.

The correct answer is Milk.

Concept:

• Dietary fibres are also known as roughage.
• Dietary fibres are mainly provided by plant products in our foods.
• It is a carbohydrate that contains indigestible plant parts or compounds of plants that pass comparatively without any change through the stomach and the intestines.
• Dietary fibres do not provide any nutrient to our body, but is an essential component of our food and adds to its bulk. 
• This helps our body get rid of undigested food.

Explanation:

• Milk is an animal product, whereas dietary fibre is a plant product.
• Milk does not provide dietary fibre.
• It is high in vitamins, proteins, and minerals, particularly calcium.
• Whole grains and pulses, whole potatoes, fresh fruits and vegetables are the main sources of roughage or dietary fibres.

Additional Information

• A balanced diet provides all the nutrients that our body needs, in the right quantities, along with an adequate amount of roughage and water.
• The major nutrients in our food are carbohydrates, proteins, fats, vitamins and minerals. 
• In addition, food also contains dietary fibres and water.
• Carbohydrates and fats mainly provide energy to our bodies.
• Proteins and minerals are needed for the growth and maintenance of our body.
• Vitamins help in protecting our bodies against diseases.

The correct answer is 5 June.

Explanation:

• World Environment day is celebrated on 5 June every year and is the United nation's principal vehicle for encouraging awareness and action for the protection of the environment.
• In 1972 the United Nations General Assembly(UNGA) celebrated World Environment day on the first day of the Stockholm conference on the Human Environment.
• Since 1974 it has been regularly organized by the different host countries and with different themes.
• It is motto is engaging governments, businesses celebrities, and citizens to focus their efforts on a pressing environmental issue.
• The theme of first world environment day was ''only one earth"
• The theme of world Environment day 2020 was Time for nature and the host country was Colombia.
• The theme of world Environment day 2021 was ecosystem restoration and the host country was Pakistan calibration with the United Nations Environment Programme.
• the theme of this year's World Environment Day, “Only One Earth", focusing on “Living Sustainably in Harmony with Nature” and the host country is Sweden​

Additional Information

• 5 May celebrate is International midwife day
• The day focuses on the role of midwives and midwifery.
• Midwifery is skilled, knowledgable, and compassionate care for childbearing women newborn infants, and families throughout pre-pregnancy, birth postpartum, and the early weeks of life.
• 15 September is the anniversary of M.Visvesvaraya, and it's celebrated as Engineer's day.​​​

The correct answer is 2.25 × 108 ms-1.

Key Points

Important Points

• Refractive Index is a value calculated from the ratio of the speed of light in a vacuum or air to that in a second medium of greater density. 

• where n is the refractive index, c is the velocity of light in a vacuum ( 3 × 108 m/s), v is the velocity of light in a medium.
• The refractive index is dimensionless.
• The vacuum has a refractive index is 1.

Additional Information

• Study of light - Optics. 
• Light is a transverse wave.
• Light travels faster in Vacuum.
• Speed of light - 3 x 108 ms-1.
• Time is taken by sunlight to reach earth - 8 minutes 20 seconds (500 seconds).
• Time is taken by moonlight to reach earth - 1.28 seconds.

The correct answer is Grass, Goat and Human.

Concept:

• Food chain: 
  • A food chain depicts the feeding relationship between various organisms in a specific environment.
  • The transfer of energy from producers to top consumers, and from consumers to decomposers through a series of organisms is called a food chain.
  • Each step or level of the food chain forms a trophic level.
  • The autotrophs or the producers are at the first trophic level.
  • The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third, and larger carnivores or the tertiary consumers form the fourth trophic level.

Explanation:

• Primary producers: (Autotrophs)
  • Primary producers are at the first tropic level.
  • They produce food on their own with the help of photosynthesis. 
  • Example: plants, trees, grass.
• Primary Consumers (Heterotrophs)
  • Primary Consumers are the herbivore's animals, whose nutrition is directly based on plant products. 
  • Example- Goat, cow, deer, grasshoppers.
• Secondary consumers
  • Secondary consumers are carnivorous animals that eat meats whether it is of live animals or dead ones.
  • Example- small birds, wolfs, humans etc.
• Tertiary Consumers
  • Tertiary Consumers are also carnivorous but they feed on secondary consumers.

Additional Information
Two types of food chains can be observed in the ecosystem:

• Grazing food chain (GFC):
  • It starts with green plants called producers as the first trophic level.
  • Energy for the food chain comes from the sun.
  • Example: Grass → Goat→ Human
• Detritus food chain (DFC):
  • It begins with dead organic matter and decomposers called saprophytes at the first trophic level.
  • Energy for the food chain comes from organic remains or detritus.
  • Example: Dead leaves →  Woodlouse → Blackbird

CONCEPT:

• Magnetic field/magnetic induction (B): The region around a magnet in which another magnet experiences a magnetic force is called magnetic induction.
  • It is also called magnetic flux density.
  • The SI unit is Tesla.
• Magnetic flux (Φ): The number of magnetic field lines passing a surface area is called magnetic flux.
  • The SI unit is weber.

Φ = B.A

• Where B is magnetic induction/magnetic field/magnetic flux density, and A is area

EXPLANATION:

• The SI unit of magnetic induction is the tesla (T). So option 3 is correct.

Additional Information

1 Tesla (T) = 1 weber per square meter = 1 Wb/m²

The correct answer is Sublimation.

Key Points

Sublimation:

• Sublimation is defined as the transition of a substance from the solid phase to the gaseous phase without changing into the liquid phase.
• This process is an endothermic phase transition that occurs at a temperature and pressure below the triple point of the substance.
• Desublimation or deposition is the reverse of this process in which a gas is directly converted into a solid state.
• The best example of sublimation is dry ice which is a frozen form of carbon dioxide.
  • When dry ice gets exposed to air, dry ice directly changes its phase from a solid state to a gaseous state which is visible as fog.
  • Frozen carbon dioxide in its gaseous state is more stable than in its solid state.

Important Points

• Another well-known example of sublimation is naphthalene which is an organic compound.
  • Naphthalene is usually found in pesticides such as mothballs.
  • This organic compound sublimes due to the presence of non-polar molecules that are held by Van Der Waals intermolecular forces.
  • At a temperature of 176°F naphthalene sublimes to form vapours. It desublimates at cool surfaces to form needle-like crystals.

• The ph value of the acid in the stomach is 1.5 - 2.5.
• The acidic environment of the stomach helps in the process of breaking down of the food particles.
• The acid present in the stomach is Hydrochloric Acid (HCL).
• HCl provides the acidic pH (pH 1.8) optimal for pepsins.