Search Previous Year Questions

The correct answer is Negative, as it is below the axis.

Key Points

• According to the New Cartesian Sign Convention, the principal axis of the lens is treated as the X-axis, and the optical center is treated as the origin.
• Distances measured perpendicular to and above the principal axis (along the positive Y-axis) are taken as positive.
• Distances measured perpendicular to and below the principal axis (along the negative Y-axis) are taken as negative.
• A real image formed by a spherical lens is always inverted relative to the object.
• Since an inverted image is oriented downwards below the principal axis, its height (h') is mathematically assigned a negative sign. Hence, the statement is correct.

 Additional Information

• Magnification (m):
• It is the ratio of the height of the image (h') to the height of the object (h), expressed as m = h'/h.
• For real and inverted images, the magnification value is always negative because h' is negative and h is positive.
• For virtual and erect images, the height h' is positive, resulting in a positive magnification value.
• Image Characteristics:
• Real Images: Formed by the actual convergence of light rays and can be obtained on a screen.
• Virtual Images: Formed when light rays appear to diverge from a point; they are always erect and cannot be caught on a screen.
• Object Height: By convention, the object is usually placed above the principal axis, so the object height (h) is typically considered positive.

The correct answer is Negative, as it opposes the initial motion.

Key Points

• When an object is projected vertically upwards, its initial velocity (u) is directed in the upward direction.
• The acceleration due to gravity (g) is a constant force that always acts downwards, directed toward the center of the Earth.
• In the standard Cartesian sign convention for kinematics, the direction of the initial displacement or velocity is typically considered positive. Since the acceleration vector (gravity) is opposite to the direction of the initial upward velocity, it is taken as negative.
• This negative acceleration acts as a retardation (deceleration), causing the object's speed to decrease uniformly until it reaches zero at the highest point of its flight.
• Applying this to the equations of motion, the variable a is substituted with −g to accurately model the slowing down of the object as it rises against the pull of gravity.

 Additional Information

• Modified Equations of Motion: For upward vertical motion, the standard formulas change as follows:
• \( v = u − gt \)
• \( h = ut − \frac{1}{2}gt^{2} \)
• \( v^{2} = u^{2} − 2gh \)
• Acceleration due to Gravity (g): On Earth, its average value is 9.8 m/s². While the magnitude is constant near the surface, its vector direction is the defining factor for the sign in equations.
• Maximum Height: At this point, the final velocity (v) is 0. The time taken to reach this height is calculated as t = u/g.
• Downward Motion: If the object is dropped from a height, the initial velocity and acceleration are in the same direction (downwards), and thus both are usually taken as positive or negative depending on the chosen frame of reference.

The correct answer is Carbon dioxide uptake occurs at night and carbohydrates are synthesized during the day..

Key Points

• Desert plants, categorized as Xerophytes, utilize a specialized photosynthetic adaptation known as Crassulacean Acid Metabolism (CAM) to survive in extremely arid conditions.
• To prevent excessive water loss through Transpiration, these plants keep their Stomata tightly closed during the day when temperatures are high.
• At night, the Stomata open to take in Carbon Dioxide (CO2) from the atmosphere, which is then fixed into Malic Acid and stored in the cell Vacuoles.
• During the following day, the stored Malic Acid is transported out of the vacuole and broken down to release Carbon Dioxide internally within the leaf cells.
• This internal CO2 is then processed through the Calvin Cycle using the energy (ATP and NADPH) generated by the Light-Dependent Reactions occurring in the Chloroplasts.
• This temporal separation of Carbon Fixation and the Calvin Cycle ensures the plant can perform photosynthesis while conserving maximum water.

 Additional Information

• Photosynthetic Pathways:
• C3 Plants: Fix carbon directly into a 3-carbon compound during the day; they are common in temperate regions but lose significant water in heat.
• C4 Plants: Separate carbon fixation and the Calvin cycle spatially in different cell types (Mesophyll and Bundle Sheath cells).
• CAM Plants: Examples include Cacti, Pineapples, Agave, and Aloe Vera, which separate these processes by time (Night vs. Day).
• Ecological Importance:
• The Water-Use Efficiency (WUE) of CAM plants is significantly higher than that of C3 or C4 plants, allowing them to inhabit regions where Precipitation is scarce.
• The Waxy Cuticle on the surface of these plants further assists in reducing non-stomatal water loss.

The correct answer is 2 m.

Key Points

• The physical relationship between the velocity of a wave, its frequency, and its wavelength is defined by the fundamental wave equation: v = f × λ. This principle applies to all periodic waves, including acoustic and electromagnetic waves.
• The frequency (f) of the sound wave is given as 220 Hz. In physics, frequency represents the number of cycles or vibrations that occur in one second. The unit Hertz (Hz) is equivalent to s⁻¹.
• The speed of sound (v) in the specific medium is provided as 440 m/s. The speed of a wave depends on the density and elasticity of the medium through which it travels.
• To solve for the wavelength (λ), the equation is rearranged to λ = v / f. Wavelength is the spatial distance between two consecutive corresponding points of the wave, such as two compressions or rarefactions.
• By substituting the given values: λ = 440 / 220. Dividing the velocity by the frequency yields a result of 2 m. This means the wave repeats its pattern every 2 meters in that medium.

 Additional Information

• Sound Waves:
• Sound is a mechanical wave that requires a material medium (solid, liquid, or gas) for propagation. It is characterized as a longitudinal wave because the particles of the medium oscillate parallel to the direction of wave motion.
• In air at standard room temperature (20°C), the speed of sound is approximately 343 m/s, whereas it is significantly faster in liquids like water (approx. 1480 m/s) and solids like iron (approx. 5120 m/s).
• Human Audibility:
• The standard audible range for human beings is between 20 Hz and 20,000 Hz. The frequency in this problem (220 Hz) falls well within this range and corresponds to a relatively low pitch.
• Frequencies below 20 Hz are termed infrasonic, while those above 20 kHz are termed ultrasonic.
• Wavelength and Energy:
• In a given medium, because wave speed is constant for a specific set of conditions, the wavelength is inversely proportional to the frequency. Therefore, higher frequency sounds have shorter wavelengths.

The correct answer is Prokaryotic Cell.

Key Points

• The analogy compares a cellular structure to the specific category of organism it characterizes. A Nucleus is a membrane-bound organelle that contains the genetic material and is the hallmark of a Eukaryotic Cell.
• Similarly, a Nucleoid is the region within a Prokaryotic Cell where the primary DNA is located. Unlike the nucleus, the nucleoid is not enclosed by a nuclear envelope or membrane.
• The Nucleoid typically contains a single, circular chromosome consisting of double-stranded DNA, which is essential for the growth, survival, and reproduction of prokaryotes like Bacteria.
• While eukaryotes compartmentalize their genome within a nucleus to protect it and regulate gene expression, prokaryotes maintain their genetic information in the Nucleoid, allowing for efficient transcription and translation in the cytoplasm.

 Additional Information

• Cellular Categories:
• Prokaryotic Cells: These are generally unicellular organisms belonging to the domains Bacteria and Archaea. They lack membrane-bound organelles and possess 70S Ribosomes.
• Eukaryotic Cells: These include Plant Cells, Animal Cells, and Fungi. They are characterized by a Nucleus, Mitochondria, and a complex cytoskeleton.
• Multicellular Organisms:
• These organisms consist of many Eukaryotic Cells working in coordination. Since they are composed of eukaryotic units, they contain Nuclei rather than nucleoids.
• Microscopic Scale:
• Prokaryotes are significantly smaller, typically ranging from 0.1 to 5.0 micrometers in diameter, whereas Eukaryotes range from 10 to 100 micrometers.

The correct answer is To neutralise the acid formed in the mouth after eating food.

Key Points

• The mouth contains various bacteria that break down food particles, specifically sugars and carbohydrates, into organic acids such as lactic acid through fermentation.
• Tooth enamel is the hardest substance in the human body, composed of calcium hydroxyapatite (a crystalline form of calcium phosphate), but it begins to corrode when the pH level in the mouth falls below 5.5.
• Toothpaste is formulated to be mildly basic (alkaline) to counteract the acidic environment created by bacterial activity.
• The interaction between the basic toothpaste and the acidic residues in the mouth is a neutralization reaction, which results in the formation of salt and water, effectively raising the pH level.
• By neutralizing these acids, toothpaste prevents the demineralization of enamel, thereby protecting the teeth from cavities, dental caries, and long-term decay.

 Additional Information

• Chemical Components of Toothpaste:
• Fluoride: Most toothpastes contain sodium fluoride or stannous fluoride, which aids in remineralization by creating fluorapatite, a substance more resistant to acid than hydroxyapatite.
• Abrasives: Ingredients like calcium carbonate and hydrated silica help physically remove plaque and food debris from the tooth surface.
• The pH Scale:
• The pH scale ranges from 0 to 14; a value of 7 is neutral, values below 7 are acidic, and values above 7 are basic (alkaline).
• A basic medium (like toothpaste) accepts hydrogen ions (H⁺) or provides hydroxide ions (OH⁻) to neutralize acidity.
• Saliva Function:
• Human saliva has a natural buffering capacity and a slightly acidic to neutral pH (approx. 6.2 to 7.6), but it cannot always keep up with the rapid acid production after consuming high-sugar foods.

The correct answer is Chemicals persist and accumulate via biomagnification.

Key Points

• Biomagnification, also known as biological magnification, is the process where the concentration of toxic substances increases significantly as they move up through successive trophic levels in a food chain.
• Many modern pesticides and industrial chemicals are non-biodegradable and biopersistent, meaning they do not break down easily through natural biological or chemical processes.
• These harmful residues are typically fat-soluble (lipophilic), which allows them to be stored in the adipose tissues (fat) of organisms rather than being metabolized or excreted.
• When a predator eats multiple prey organisms, it ingests all the accumulated toxins from each individual, leading to a much higher concentration in its own body.
• Humans usually occupy the position of top consumers in various food webs, consuming a wide variety of plants and animals that have already concentrated these chemical residues.
• Because of this cumulative effect, even small amounts of chemicals sprayed on crops or released into water bodies can reach hazardous levels in human tissues.

 Additional Information

• Bioaccumulation:
• This refers to the increase in the concentration of a substance in a single organism over time, compared to the substance's concentration in the surrounding environment.
• Pesticide Persistence:
• Many organochlorines like DDT are highly stable and can remain in the ecosystem for decades, continuing to enter the food chain long after their initial application.
• Standard food processing or cooking techniques are often insufficient to destroy these synthetic compounds, as many are resistant to high heat.
• Plant Absorption:
• Plants do not selectively absorb only 'useful' chemicals; they frequently take up heavy metals (like lead and cadmium) and systemic pesticides through their root systems along with water and minerals.

The correct answer is Cartilage.

Key Points

• Cartilage is a specialized type of skeletal connective tissue characterized by a solid but pliable intercellular material that is capable of resisting compression.
• The matrix of this tissue is composed of chondroitin salts and collagen fibers, which provide both structural integrity and a degree of flexibility.
• The specific cells found in cartilage are called chondrocytes, which are enclosed in small cavities known as lacunae within the matrix they secrete.
• While most of the cartilaginous skeleton in vertebrate embryos is replaced by bone in adults, cartilage remains in critical locations such as the tip of the nose, external ear joints (pinna), and intervertebral discs.
• It also forms articular cartilage at the ends of long bones, where it provides a smooth, lubricated surface to facilitate low-friction movement within joints.

 Additional Information

• Areolar tissue:
• A common type of loose connective tissue located beneath the skin.
• It serves as a support framework for the epithelium and contains cells like fibroblasts, macrophages, and mast cells.
• Adipose tissue:
• Another type of loose connective tissue specialized for the storage of fats.
• It is found mainly beneath the skin and acts as an insulator and energy reservoir.
• Bone:
• A dense connective tissue with a hard and non-pliable ground substance.
• It is rich in calcium salts and collagen fibers, which give bone its strength to provide the primary structural frame of the body.

The correct answer is A car moving with constant speed on a straight road.

Key Points

• Acceleration is defined as the rate of change of velocity over time. It is represented by the formula a = (v − u) / t, where v is the final velocity and u is the initial velocity.
• Velocity is a vector quantity, meaning it possesses both magnitude (speed) and direction. Acceleration occurs if either the speed or the direction of motion changes.
• In the case of a car moving at a constant speed on a straight road, the magnitude of velocity is unchanging, and the direction is fixed. Therefore, the change in velocity (Δv) is zero, resulting in zero acceleration.
• According to Newton's First Law of Motion, an object moving with constant velocity has a net external force of zero acting upon it, which is consistent with the condition of zero acceleration.

 Additional Information

• Ball thrown upward:
• An object thrown vertically experiences a constant acceleration due to gravity (g), which is approximately 9.8 m/s² downward.
• Even at the peak of its trajectory where instantaneous velocity is zero, the acceleration remains non-zero.
• A train speeding up:
• When a vehicle increases its speed, it undergoes positive acceleration.
• This involves a change in the magnitude of velocity over a specific time interval.
• An aeroplane taking off:
• During a takeoff roll, an aircraft accelerates from a standstill to reach its liftoff speed.
• This represents a significant linear acceleration required to generate the necessary aerodynamic lift.
• Uniform Circular Motion:
• Even if an object moves at a constant speed in a circle, its direction changes at every point.
• This change in direction results in centripetal acceleration directed toward the center of the path.

The correct answer is Non-biodegradable pesticides accumulate at successive trophic levels.

Key Points

• Biological magnification, or biomagnification, is the process where certain toxic substances, such as pesticides or heavy metals, increase in concentration as they move up the food chain.
• These chemicals are non-biodegradable, meaning they cannot be broken down by biological processes or enzymes within an organism's body.
• Because these substances are often fat-soluble, they are not excreted through urine but are instead stored in the adipose tissues of organisms at each trophic level.
• As a predator eats multiple prey items, it ingests all the accumulated toxins from those individuals, leading to a exponentially higher concentration in the top consumers.
• Since humans occupy the highest trophic level in many ecological systems, the maximum concentration of these harmful chemicals gets accumulated in our bodies, leading to chronic health issues, reproductive failure, and hormonal imbalances.

 Additional Information

• Common Biomagnifiers:
• DDT (Dichlorodiphenyltrichloroethane): A classic example of a pesticide that caused bird eggshells to thin, leading to population declines in bald eagles.
• Mercury: Often found in aquatic ecosystems, it magnifies in fish like tuna and swordfish, posing risks to human neurological health.
• Bioaccumulation vs. Biomagnification:
• Bioaccumulation refers to the build-up of a substance within a single organism over its lifetime.
• Biomagnification refers to the increase in concentration as the substance transfers from one trophic level to the next.
• Impact on Ecosystems:
• The accumulation of toxins can disrupt the energy flow and nutrient cycling by killing off key species or reducing their reproductive success.