Bihar Board Class 10 Science(Set I - Shift 2)Question Paper 2024 (Available):Download Solution With Answer Key

The process by which water is expelled from plants through the stomata (small pores in leaves and stems) in the form of vapor is called transpiration. This process plays a crucial role in maintaining the flow of water and nutrients from the roots to the rest of the plant, and also helps in cooling the plant.

Osmosis (option A) refers to the movement of water across a semipermeable membrane from a region of low solute concentration to high solute concentration. Excretion (option C) is the process of eliminating waste materials from the body. Diffusion (option D) refers to the movement of molecules from an area of higher concentration to an area of lower concentration, but not specifically in the context of water vapor expulsion in plants. Quick Tip: Transpiration helps in cooling plants, maintaining water flow, and ensuring the uptake of minerals from the soil.

The tiger, being a carnivore, feeds on herbivores (the second trophic level). It does not consume primary producers (plants), which are at the first trophic level, nor does it consume other carnivores, which are typically at higher levels. Therefore, the tiger occupies the third trophic level as a secondary consumer. Quick Tip: In a food chain, primary consumers (herbivores) occupy the second trophic level, and secondary consumers (carnivores like the tiger) occupy the third trophic level.

Based on fossil and genetic evidence, it is widely accepted that the origin of modern humans can be traced to Africa. The "Out of Africa" hypothesis suggests that humans evolved in Africa and later migrated to other regions of the world. Quick Tip: The origin of humans is traced back to Africa according to the "Out of Africa" theory.

Peristalsis refers to the wave-like muscular contractions that move food through the digestive tract. This process is most notably found in the oesophagus, where it moves food from the mouth to the stomach. Peristalsis also occurs in other parts of the digestive system, such as the small intestine and colon. Quick Tip: Peristalsis is critical for the movement of food and liquids through the digestive system, starting from the oesophagus.

An open circulatory system, where blood is not confined to vessels but flows freely within cavities, is found in arthropods such as butterflies. In contrast, vertebrates like humans, pigeons, and cats have a closed circulatory system. Quick Tip: Arthropods like butterflies have an open circulatory system, which is different from the closed system found in vertebrates.

The protein \textit{hemoglobin in red blood cells binds with oxygen in the lungs and carries it through the blood to tissues and organs. It is the primary carrier of oxygen in the blood. Quick Tip: Hemoglobin is responsible for the red color of blood and is essential for oxygen transport.

Humans have 23 pairs of chromosomes, out of which 22 pairs are autosomes, and the remaining pair are sex chromosomes (XX or XY). Quick Tip: In humans, 22 pairs of chromosomes are autosomes, and the 23rd pair are sex chromosomes.

Red light is the most effective in driving photosynthesis, although blue light also plays an important role. Plants reflect green light, which is why they appear green to us. Quick Tip: Red and blue light are primarily used by plants for photosynthesis, while green light is reflected.

Tamarind is known to contain oxalic acid, a naturally occurring compound. It is one of the notable sources of this acid in nature, along with other plants such as spinach and rhubarb. Quick Tip: Tamarind contains a significant amount of oxalic acid, which contributes to its tart flavor.

Step 1: Understanding the structure of propane \( C_3H_8 \).

Propane consists of three carbon (\(C\)) atoms and eight hydrogen (\(H\)) atoms. The structure of propane is as follows:
\[ CH_3 - CH_2 - CH_3 \]

Step 2: Identifying the covalent bonds.

1. Each carbon forms a single bond with other carbon atoms.
2. Each carbon also forms single bonds with hydrogen atoms.
3. Carbon always forms four covalent bonds (either with carbon or hydrogen).

Step 3: Counting the bonds.

- There are 2 carbon-carbon (\(C-C\)) single bonds.
- There are 8 carbon-hydrogen (\(C-H\)) single bonds.
\[ Total covalent bonds = 2 (C-C) + 8 (C-H) = 10. \]

Thus, the total number of covalent bonds in propane is 10. Quick Tip: To determine the number of covalent bonds in an organic molecule, count all single, double, or triple bonds formed between atoms.

The ozone layer primarily absorbs and blocks ultraviolet (UV) radiation from the Sun. UV radiation can cause significant harm to living organisms, which is why the ozone layer is vital for life on Earth. Quick Tip: The ozone layer shields us from harmful UV radiation, which is why it is critical for human health and the environment.

Bromine is the only non-metal that exists as a liquid at room temperature. It is a halogen and is reddish-brown in color. Quick Tip: Bromine is a non-metal that is unique in being a liquid at room temperature.

Arsenic (As) is a metalloid, meaning it has characteristics of both metals and non-metals. Fe, Cu, and Ni are metals. Quick Tip: Metalloids, like arsenic, have properties that are intermediate between metals and non-metals.

This is a decomposition reaction where one reactant (\( CaCO_3 \)) breaks down into two products (\( CaO \) and \( CO_2 \)). Quick Tip: Decomposition reactions involve the breakdown of a single compound into two or more products.

The equation \( H_2 + Cl_2 \rightarrow HCl \) is balanced as both sides contain the same number of hydrogen and chlorine atoms. Quick Tip: Always check if the number of atoms of each element is the same on both sides of the equation for it to be balanced.

Sulphur dioxide (SO\(_2\)) is primarily responsible for acid rain. It reacts with water vapor in the atmosphere to form sulfuric acid, which contributes to acid rain. Quick Tip: Sulphur dioxide is a significant pollutant produced by industrial activities that causes acid rain.

Step 1: Understanding magnification in a concave mirror.

The magnification (\( m \)) of a concave mirror is given by: \[ m = \frac{-v}{u} \]
where:
- \( v \) is the image distance,
- \( u \) is the object distance.

For a concave mirror:
- If the image is real and inverted, the magnification is negative.
- If the image is virtual and upright, the magnification is positive.

Step 2: Condition for positive magnification.

- A concave mirror produces a positive magnification only when the image is virtual and erect.
- This happens when the object is placed between the focus (\( F \)) and the pole (\( P \)) of the mirror.
- The focal length of the mirror is given as 10 cm, meaning the focal point is at \( u = -10 \) cm.

Step 3: Finding the correct range for object distance \( u \).

- If the object is placed at \( u < 10 \) cm (i.e., between the pole and focus), the image will be virtual, upright, and magnified.
- Hence, the correct answer is (C) less than 10 cm. Quick Tip: A concave mirror produces a virtual and magnified image when the object is placed between the pole and the focus.

Step 1: Understanding magnification in a concave mirror.

The magnification (\( m \)) of a concave mirror is given by: \[ m = \frac{-v}{u} \]
where:
- \( v \) is the image distance,
- \( u \) is the object distance.

For a concave mirror:
- When the object is beyond the center of curvature (\( C \)), the image is real, inverted, and smaller (\( |m| < 1 \)).
- When the object is at \( C \), the image is of the same size (\( |m| = 1 \)).
- When the object is between \( C \) and \( F \) (focus), the image is real, inverted, and magnified (\( |m| > 1 \)).
- When the object is at \( F \), the image is formed at infinity.
- When the object is between \( F \) and \( P \) (pole), the image is virtual, upright, and highly magnified.

Step 2: Behavior of magnification as the object moves from \( F \) to \( P \).

- When the object moves from the focus towards the pole, the image remains virtual and magnified.
- The magnification increases as the object gets closer to the mirror.
- At the pole, the magnification tends to infinity.

Step 3: Conclusion.

Since magnification increases as the object moves towards the pole, the correct answer is (A) increases. Quick Tip: In a concave mirror, moving an object from the focus towards the pole increases magnification, making the image larger and more upright.

A hydro-electric power plant converts potential energy of water (stored at a height) into mechanical energy, which is then converted to electrical energy. Quick Tip: The potential energy of water in a hydroelectric plant is converted to electrical energy using turbines.

The direction of the induced current changes after one full rotation (360°), i.e., every one rotation. Quick Tip: The induced current in a rotating coil changes direction every full rotation.

In a concave mirror, when an object moves from the pole towards the focus, the image increases in size and remains erect. Quick Tip: The image formed by a concave mirror becomes larger as the object moves from the pole towards the focus.

The ciliary muscles are responsible for controlling the curvature of the lens in the eye, which enables the eye to focus on near and far objects. Quick Tip: Ciliary muscles adjust the lens shape to focus light on the retina.

Clouds appear white because light is scattered in all directions by the water droplets in the clouds. This scattering of all colors of light leads to a white appearance. Quick Tip: Scattering of light by tiny droplets or particles results in the white color of clouds.

The SI unit of resistance is the ohm (Ω), which is defined as the resistance that allows one ampere of current to flow when one volt is applied. Quick Tip: The unit of resistance, the ohm, is the reciprocal of the unit of conductance, the siemens.

The kidney plays a vital role in excretion by filtering waste materials and regulating water balance in the body. Quick Tip: Kidneys are essential for removing waste products from the blood and maintaining fluid balance in the body.

Photosynthesis occurs only in the presence of light, so it happens during the day when sunlight is available. Quick Tip: Photosynthesis is a process that requires sunlight, so it only takes place during the day.

Synaptic knobs, or axon terminals, are found at the ends of neurons and are responsible for transmitting nerve signals. Quick Tip: Synaptic knobs release neurotransmitters that enable communication between neurons.

Rats have the fastest heartbeat among the listed animals, with a heart rate that can exceed 500 beats per minute. Quick Tip: Smaller animals generally have higher heart rates than larger animals.

Glucose is the primary fuel for cellular respiration. It is broken down in cells to release energy. Quick Tip: Glucose is the main energy source for cells in the body, used to produce ATP.

ATP contains three phosphate groups, which are essential for storing and transferring energy within cells. Quick Tip: ATP is the primary energy source in cells, and it has three phosphate groups.

The pancreas is not involved in excretion; it is an endocrine and digestive organ. The lungs, kidneys, and skin are involved in excretion. Quick Tip: The pancreas is important for digestion and regulating blood sugar, not excretion.

The pineal gland is the smallest endocrine gland, located in the brain, and is responsible for producing melatonin. Quick Tip: The pineal gland, though small, plays a key role in regulating sleep patterns.

Acids release H\(^+\) ions (protons) when they dissolve in water, which is what makes the solution acidic. Quick Tip: The presence of H\(^+\) ions is what defines a substance as acidic.

Acetic acid (CH\(_3\)COOH) is a weak acid because it partially dissociates in water, unlike HCl, H\(_2\)SO\(_4\), and HNO\(_3\), which are strong acids. Quick Tip: Weak acids like acetic acid dissociate only partially in water.

Silver iodide (AgI) appears yellow in color due to its crystal properties. Quick Tip: Silver iodide is used in photographic films and has a distinctive yellow color.

Diamond is the hardest known natural substance, with the highest rating on the Mohs scale of hardness. Quick Tip: Diamond has the highest hardness of any known natural substance.

Carbon has three crystalline allotropes: diamond, graphite, and graphene. Quick Tip: Diamond, graphite, and graphene are the three crystalline forms of carbon.

Zinc blende (ZnS) is an ore of zinc. Quick Tip: Zinc blende is the primary ore from which zinc is extracted.

In a nitrogen molecule (N\(_2\)), the two nitrogen atoms are bonded by a triple bond, which consists of three shared electron pairs. Quick Tip: Nitrogen gas (N\(_2\)) has a triple bond between the two nitrogen atoms.

The general formula for alkynes, which have a triple bond, is C\(_n\)H\(_{2n-2}\). Quick Tip: Alkynes contain at least one triple bond and have the general formula C\(_n\)H\(_{2n-2}\).

Kilowatt-hour (kWh) is a unit of energy, specifically used to quantify electrical energy consumption. Quick Tip: Kilowatt-hour is the standard unit for measuring electrical energy.

Step 1: Understanding the function of the iris in the human eye.

- The iris is the colored part of the eye that surrounds the pupil.
- It contains muscles that contract or relax to adjust the size of the pupil.
- The pupil regulates the amount of light entering the eye.

Step 2: Why the iris controls light entry.

- In bright light, the iris constricts, making the pupil smaller to limit the amount of light entering.
- In dim light, the iris expands, making the pupil larger to allow more light in.
- This automatic adjustment helps protect the retina from excessive light and ensures clear vision.

Step 3: Analyzing the options.

- Ciliary muscles (Option A): Control the shape of the lens for focusing, not light entry.
- Pupil (Option B): It is the opening through which light enters, but the iris controls its size.
- Cornea (Option C): It helps focus light onto the retina but does not control the amount of light entering.
- Iris (Option D): It adjusts the pupil size to control light entry.

Conclusion: Since the iris controls the amount of light entering the eye, the correct answer is (D) iris. Quick Tip: The iris controls the size of the pupil, which regulates the amount of light entering the eye, ensuring proper vision.

Biomass, which includes wood, agricultural residues, and animal waste, is considered a conventional energy source used for heating and cooking. Quick Tip: Biomass has been used historically for energy production and is considered a conventional energy source.

The maximum number of electrons that can be held in a shell is \( 2n^2 \), where \( n \) is the shell number. Quick Tip: The formula for the maximum number of electrons in a shell is \( 2n^2 \).

Methane (CH\(_4\)) is the simplest hydrocarbon because it contains only one carbon atom bonded to four hydrogen atoms. Quick Tip: Methane is the simplest alkane and the main component of natural gas.

Sodium (Na) has the lowest melting point among these metals, at approximately 98°C. Quick Tip: Sodium has the lowest melting point among alkali metals.

Gold (Au) has an atomic number of 79. Quick Tip: Gold is an element with the atomic number 79 and is represented by the symbol Au.

K\(_2\)SO\(_4\) is a salt formed by the reaction between a strong acid (H\(_2\)SO\(_4\)) and a strong base (KOH). Quick Tip: Salts are formed from the neutralization of acids and bases.

CFCs (Chlorofluorocarbons) are compounds that release chlorine atoms when they break down in the stratosphere, causing the depletion of the ozone layer. Quick Tip: CFCs are harmful to the ozone layer and have been banned in many countries due to their environmental impact.

Yeast undergoes asexual reproduction through budding, where a small bud forms on the parent organism and eventually detaches to form a new individual. Quick Tip: Budding is a form of asexual reproduction observed in organisms like yeast and hydra.

IAA (Indole-3-acetic acid) is a naturally occurring plant hormone responsible for regulating growth. Quick Tip: IAA is a type of auxin that helps in cell growth and elongation in plants.

Potatoes propagate vegetatively through their tubers, which are modified stems that can give rise to new plants. Quick Tip: Tubers are specialized stem structures that allow potatoes to reproduce vegetatively.

Hydrilla is an aquatic plant commonly found in freshwater environments. Quick Tip: Hydrilla is a submerged aquatic plant that thrives in shallow freshwater habitats.

Normal systolic blood pressure in a healthy adult is typically around 120 mm Hg, which is the upper value of the blood pressure reading. Quick Tip: Systolic blood pressure represents the pressure in the arteries when the heart contracts.

Hydra is a bisexual organism capable of producing both male and female gametes, allowing for self-fertilization. Quick Tip: Bisexual organisms can produce both male and female reproductive cells.

Fish use gills to extract oxygen from water. Water flows over the gills, and oxygen is absorbed while carbon dioxide is expelled. Quick Tip: Fish use gills for gas exchange in water, unlike land animals that use lungs.

Elements in the same group of the periodic table have the same number of valence electrons and, therefore, the same valency. Quick Tip: Elements in the same group have the same valency due to similar electron configurations.

Wine contains ethanol, which is a type of alcohol produced during fermentation. Quick Tip: Ethanol is the type of alcohol present in alcoholic beverages like wine.

Step 1: Understanding Group 3 of the Periodic Table.

- The third group of the periodic table includes elements from both the main group and transition series.
- It consists of Scandium (Sc), Yttrium (Y), Lanthanum (La), and Actinium (Ac) as well as elements from the lanthanide and actinide series.

Step 2: Counting the elements.

- Scandium (Sc) and Yttrium (Y) are always included.
- The inclusion of Lanthanum (La) and Actinium (Ac) follows the periodic trends.
- The lanthanides and actinides also belong to the third group, leading to a total count of 8 elements.

Step 3: Conclusion.

- Since the total number of elements in Group 3 is 8, the correct answer is (D) 8. Quick Tip: Group 3 of the periodic table contains 8 elements, including transition metals and some lanthanides and actinides.

Silicon is the primary material used in the production of solar cells due to its excellent semiconducting properties. Quick Tip: Silicon is the key component in most solar cells because of its semiconductor nature.

The atomic number is the total number of electrons in an atom. With the configuration 2, 8, 7, the atomic number is 17. Quick Tip: The atomic number corresponds to the number of electrons or protons in an element.

Duralumin is an alloy primarily composed of aluminum (Al) and small amounts of copper and other elements. Quick Tip: Duralumin is a strong and light alloy made of aluminum and copper.

Sodium phosphate has the formula Na\(_3\)PO\(_4\), with three sodium ions balancing the charge of the phosphate ion. Quick Tip: Sodium phosphate is used in detergents and as a food additive.

The nephron is the functional unit of the kidney, involved in filtering the blood and producing urine. Quick Tip: Each kidney contains millions of nephrons that perform the essential tasks of filtration.

A wind speed of at least 15 km/h is required for a wind electric generator to begin generating electricity. Quick Tip: Wind turbines typically begin generating electricity at speeds above 15 km/h.

A split ring is used in D.C. motors as a commutator to reverse the current direction and ensure continuous rotation. Quick Tip: Split rings are crucial components in D.C. motors for current reversal.

In metallic conduction, free electrons move through the lattice, transferring energy and enabling electrical conductivity. Quick Tip: Electrons are the charge carriers in metallic conduction.

The glass cover of a box-type solar cooker helps to trap the heat inside and prevent it from escaping, thus reducing heat loss due to radiation. This is important for efficient cooking. Quick Tip: The glass cover allows sunlight to pass through and prevents heat loss, making the cooker more effective.

When two resistors are connected in series, the equivalent resistance \(R_{eq}\) is the sum of individual resistances. Using the formula \(R = \frac{V^2}{P}\) for each resistor, the equivalent resistance becomes:
\[ R_{eq} = \frac{V_1^2}{P_1} + \frac{V_2^2}{P_2} \] Quick Tip: For resistors in series, the total resistance is the sum of individual resistances.

In most countries, the alternating current (AC) supplied to households has a frequency of 50 Hz. Quick Tip: The standard frequency for AC supply in many countries is 50 Hz.

Step 1: Understanding refractive index.

The refractive index (n) of a medium determines how much light bends when it enters the medium from air. A lower refractive index means light bends less.

Step 2: Comparing refractive indices.

The approximate refractive indices of the given substances are:
- Water: \( n \approx 1.33 \) (Lowest)
- Kerosene: \( n \approx 1.44 - 1.48 \)
- Benzene: \( n \approx 1.50 \)
- Turpentine: \( n \approx 1.47 \)

Step 3: Conclusion.

- Water has the lowest refractive index among the given options.
- Hence, the correct answer is (C) Water. Quick Tip: A lower refractive index means the medium is less optically dense, allowing light to travel faster through it.

Step 1: Understanding the structure of a simple prism.

A prism is a transparent optical element with flat, polished surfaces that refract light. A triangular prism, which is the simplest type of prism, consists of:
1. Two triangular faces (base surfaces).
2. Three rectangular faces (lateral surfaces).

Step 2: Counting the total surfaces.

- The prism has two triangular faces (top and bottom).
- It also has three rectangular lateral faces.
\[ Total surfaces = 2 + 3 = 5 \]

Step 3: Conclusion.

Since a simple prism is bounded by 5 surfaces, the correct answer is (C) 5. Quick Tip: A simple triangular prism is enclosed by two triangular bases and three rectangular lateral surfaces, making a total of 5 surfaces.

Step 1: Understanding the far point of normal vision.

The far point of vision is the maximum distance at which an object can be seen clearly without accommodation.

For a person with normal vision, the farthest distance they can see clearly is infinity.

Step 2: Analyzing the options.

- 25 mm (Option A): This is extremely short and incorrect.
- 25 cm (Option B): This is incorrect; this is closer to the near point of vision.
- 25 m (Option C): This is incorrect, as normal vision extends far beyond this range.
- Infinity (Option D): This is correct because a normal human eye can focus on objects at an infinite distance.

Step 3: Conclusion.

- The far point for normal vision is at infinity.
- Hence, the correct answer is (D) infinity. Quick Tip: For a person with normal vision, the farthest point they can see clearly without accommodation is at infinity.

If the magnification is negative, the image formed is real and inverted. This occurs for real objects placed outside the focal point in concave mirrors. Quick Tip: Negative magnification indicates an inverted and real image.

There are two laws of reflection: 1) The angle of incidence equals the angle of reflection, and 2) The incident ray, reflected ray, and normal lie in the same plane. Quick Tip: The two laws of reflection are: 1) angle of incidence = angle of reflection, and 2) all rays lie in the same plane.

When the ray of light is perpendicular to the mirror, the angle of incidence is 0°, so the angle of reflection will also be 0°. Quick Tip: The angle of reflection is always equal to the angle of incidence.

Blue light scatters more than other colors due to its shorter wavelength, causing the sky to appear blue. Quick Tip: Shorter wavelengths like blue light scatter more, making the sky blue.

A converging lens is a convex lens that focuses parallel light rays towards a single point. Quick Tip: Converging lenses are typically convex lenses.

If half of the concave mirror is missing, the intensity of the image decreases, but the nature of the image remains unchanged. Quick Tip: A broken concave mirror reduces the intensity of the formed image.

When light moves from a rarer medium (air) to a denser medium (glass), it slows down and bends towards the normal. Quick Tip: Light bends towards the normal when moving into a denser medium.