ICSE Class 8 Physics Sample Paper with Solutions Set 02

Question 1
Choose the correct answer out of the four available choices given under each question. [15]

1. The fluid between the retina and the lens is called [1 Mark]
(a) Aqueous humour
(b) Vitreous humour
(c) Choroid
(d) Sclerotic

Answer: (b) Vitreous humour

A fluid called vitreous humour is present between the lens and the retina of the eyes which keeps it wet.

Teacher's Note:
a) Aqueous humour is the fluid located in the anterior chamber between the cornea and the lens.
b) Vitreous humour fills the posterior cavity behind the lens to maintain the shape of the eyeball.

2. Which among the following is false? [1 Mark]
(a) A denser liquid exerts a greater upthrust
(b) Relative density has no unit
(c) Icebergs have 11/12 parts above water
(d) A body experiences a loss in weight in a liquid

Answer: (c) Icebergs have 11/12 parts above water

Icebergs actually have about 11/12 parts below water and only 1/12 part above water due to density differences.

Teacher's Note:
a) Upthrust is directly proportional to the density of the liquid (\( F_u = V \rho g \)).
b) Relative density is a ratio of two similar quantities, making it a unitless quantity.

3. The attractive property of a magnet is maximum at [1 Mark]
(a) The North Pole only
(b) The South Pole only
(c) Both the poles
(d) The centre of the magnet

Answer: (c) Both the poles

The attractive property of a magnet is concentrated at its two poles, namely the North Pole and the South Pole.

Teacher's Note:
a) Magnetic strength is minimum or almost zero at the magnetic equator or centre of the magnet.
b) Iron filings cling in maximum quantities near both ends (poles) of a bar magnet.

4. Which of the following was the first satellite launched by India? [1 Mark]
(a) EDUSAT
(b) INSAT
(c) Bhaskara
(d) Aryabhatta

Answer: (d) Aryabhatta

Aryabhatta was India's first unmanned scientific earth satellite, launched on April 19, 1975.

Teacher's Note:
a) It was named after the famous ancient Indian astronomer and mathematician Aryabhatta.
b) Students must remember key historical milestones in India's space program.

5. When an object is placed beyond 2F in front of a convex lens, the image is formed [1 Mark]
(a) Between O and F
(b) At 2F
(c) Between F and 2F
(d) Beyond 2F

Answer: (c) Between F and 2F

For a convex lens, when the object is beyond \( 2F_1 \), the real and inverted image is formed between \( F_2 \) and \( 2F_2 \) on the other side.

Teacher's Note:
a) Practice all six standard ray diagram positions for convex and concave lenses.
b) The size of the image formed in this case is diminished.

6. According to the principle of calorimetry [1 Mark]
(a) Heat lost by a hot body is less than the heat gained by a cold body
(b) Heat lost by a hot body is more than the heat gained by a cold body
(c) Heat lost by a hot body is equal to the heat gained by a cold body
(d) None of the above

Answer: (c) Heat lost by a hot body is equal to the heat gained by a cold body

By the law of conservation of energy applied to heat exchange, total heat lost equals total heat gained in an isolated system.

Teacher's Note:
a) This assumes no heat is lost to the surrounding environment or the calorimeter vessel unless specified.
b) This principle forms the numerical foundation for calorimetry problems.

7. In a simple barometer, a vacuum is created in the tube above the mercury level. This vacuum is known as a [1 Mark]
(a) Barometric vacuum
(b) Torricellian vacuum
(c) Aneroid vacuum
(d) Pascalian vacuum

Answer: (b) Torricellian vacuum

The space above the mercury column in a standard Torricelli barometer contains almost no air and is called a Torricellian vacuum.

Teacher's Note:
a) Evangelista Torricelli invented the mercury barometer in 1643.
b) This space is not a perfect vacuum because it contains a small amount of saturated mercury vapour.

8. What happens to the kinetic energy of a body when 3/4th of its mass is removed and its velocity is doubled? [1 Mark]
(a) Becomes 4 times
(b) Becomes 1/4 times
(c) Becomes 1/2 times
(d) Remains the same

Answer: (d) Remains the same

Initial KE \( = \frac{1}{2}mv^2 \). New mass \( m' = m - \frac{3}{4}m = \frac{1}{4}m \). New velocity \( v' = 2v \). New KE \( = \frac{1}{2}\left(\frac{1}{4}m\right)(2v)^2 = \frac{1}{8}m \times 4v^2 = \frac{1}{2}mv^2 \).

Teacher's Note:
a) Always write down formulas clearly before substituting modified values.
b) Doubling velocity quadruples the velocity term (\( 4v^2 \)), which exactly compensates for the reduction in mass to one-fourth.

9. The quantity which mains the same across all the resistances when they are connected in a series is the [1 Mark]
(a) Current
(b) Voltage
(c) Power
(d) Heat energy

Answer: (a) Current

In a series circuit, there is only a single path for charge flow, so the electric current passing through every resistor is identical.

Teacher's Note:
a) In contrast, potential difference (voltage) divides across resistors connected in series based on their resistance values.
b) Note the typographical error in the paper ("mains" instead of "remains").

10. Who discovered that a magnetic field is developed around a current carrying conductor? [1 Mark]
(a) Michael Faraday
(b) Hans Oersted
(c) John Fleming
(d) James Maxwell

Answer: (b) Hans Oersted

Hans Christian Oersted accidentally discovered the magnetic effect of electric current in 1820 when a compass needle deflected near a live wire.

Teacher's Note:
a) Michael Faraday discovered electromagnetic induction.
b) Oersted's experiment proved the fundamental link between electricity and magnetism.

11. A prism is said to be in minimum deviation when [1 Mark]
(a) Angle of incidence = Angle of emergence
(b) Angle of incidence > Angle of emergence
(c) Angle of incidence < Angle of emergence
(d) Angle of incidence = \( 0^{\circ} \)

Answer: (a) Angle of incidence = Angle of emergence

When a ray passes through a prism symmetrically, the angle of incidence equals the angle of emergence, resulting in minimum deviation.

Teacher's Note:
a) Under this condition, the refracted ray inside the prism runs parallel to its base.
b) This condition is frequently used in optical experiments to calculate the refractive index of prism glass.

12. Which among these is not true for a solid? [1 Mark]
(a) Molecules are very tightly packed.
(b) Molecules attract one another with a strong force.
(c) It is easy to break solids as they have a strong intermolecular force.
(d) They have a definite shape and volume.

Answer: (c) It is easy to break solids as they have a strong intermolecular force

Strong intermolecular forces make solids rigid and hard to break, not easy to break. Hence statement (c) is false.

Teacher's Note:
a) Solids possess strong cohesive forces and high rigidity.
b) Read all options carefully before concluding, as option (c) contradicts the premise of strong forces.

13. Which of these functions is not performed by a gold leaf electroscope? [1 Mark]
(a) To detect a charge
(b) To differentiate between a conductor and an insulator
(c) To charge an uncharged body
(d) To identify the nature of a charge

Answer: (c) To charge an uncharged body

A gold leaf electroscope is a detecting instrument, not a charging source to power or charge up external neutral bodies.

Teacher's Note:
a) An electroscope can detect presence, estimate magnitude, and test the nature (positive or negative) of a charge.
b) It can also distinguish between good and poor conductors of electricity.

14. The temperature of the surface of the Sun is about [1 Mark]
(a) 1 million \( ^{\circ}\text{C} \)
(b) 6000 \( ^{\circ}\text{C} \)
(c) 20 million \( ^{\circ}\text{C} \)
(d) 4000 \( ^{\circ}\text{C} \)

Answer: (b) 6000 \( ^{\circ}\text{C} \)

The effective surface temperature (photosphere) of the Sun is approximately \( 6000^{\circ}\text{C} \) (around \( 5500^{\circ}\text{C} \) to \( 6000^{\circ}\text{C} \)).

Teacher's Note:
a) The core temperature of the Sun is much higher, around 15 to 20 million degrees Celsius.
b) Memorise solar temperature parameters accurately as factual questions appear frequently.

15. The main constituent of biogas is [1 Mark]
(a) Methane
(b) Ethylene
(c) Hydrogen and oxygen
(d) Oxygen and Ethane

Answer: (a) Methane

Biogas is produced by anaerobic decomposition of biomass and consists mainly of 45% to 70% methane gas.

Teacher's Note:
a) Methane is a clean-burning fuel that accounts for the high calorific value of biogas.
b) Carbon dioxide and minor traces of other gases make up the rest of the mixture.

Question 2

(A) Match the columns and rewrite them correctly. [5 Marks]

Teacher's Note:
a) Water wets glass due to adhesive forces, forming a concave meniscus.
b) Myopia (short-sightedness) is corrected using a diverging concave lens.

(B) Fill up the blanks and rewrite the sentences: [5 Marks]
1. Rainbow is produced due to _________ of white light.
2. We use water in hot bags for __________ because it will keep us warm.
3. A glass slab appears to be ________ in water than in air.
4. The __________ Pole of the Earth’s magnet is closer to the geographic South Pole.
5. If the Moon is in the ___________ core of the Earth’s shadow, it is known as a total lunar eclipse.

Answer:
1. dispersion
2. fomentation
3. lighter
4. North
5. umbral

Teacher's Note:
a) Water has a high specific heat capacity, making it ideal for fomentation in hot water bags.
b) Real apparent depth concepts explain why a glass slab appears thinner or lighter when submerged in water.

Question 3

(A) State whether the following statements are True or False. Correct the false statement and rewrite it. [5 Marks]
1. A concave lens always forms an inverted image.
2. A camel can run faster in deserts than a horse.
3. Non-renewable sources of energy can never get exhausted.
4. While charging by induction, there is no loss of charge.
5. An electromagnet is a temporary magnet.

Answer:
1. False. Corrected statement: A concave lens always forms an erect image.
2. True.
3. False. Corrected statement: Non-renewable sources of energy can get exhausted if not judiciously used.
4. True.
5. True.

Teacher's Note:
a) Concave lenses always produce virtual, erect, and diminished images irrespective of object position.
b) Always write both the True/False status and the fully corrected sentence to secure full marks.

(B) Give reasons for the following. [5 Marks]
1. It takes some time to see objects in a cinema hall when we just enter it from bright sunlight.
2. Heavy trucks have 6-8 tyres.
3. In a hydroelectric power plant more electrical power can be generated if the water falls from a greater height.
4. Soaps and detergents help in cleaning clothes.
5. Land breeze is set up during the night.

Answer:
1. The pupil of the eye regulates light entry. In bright sunlight, the pupil is constricted (small). Upon entering a dark cinema hall, it takes time for the pupil to expand (dilate) to admit sufficient light.
2. Heavy trucks have 6-8 tyres to increase the total area of contact with the ground, which reduces the pressure exerted on the road surface.
3. Greater height provides higher gravitational potential energy, which converts into greater kinetic energy of falling water to rotate turbines with higher power output.
4. Soaps and detergents lower the surface tension of water, enabling it to wet fabrics thoroughly, penetrate pores, and emulsify grease and dirt.
5. At night, land cools faster than the sea. Warmer air over the sea rises, and cooler air from the land flows towards the sea, setting up a land breeze.

Teacher's Note:
a) Scientific reasons require clear cause-and-effect explanations using physics principles like pressure, surface tension, and energy transformation.
b) Ensure all sub-parts are answered concisely with key scientific terms.

Question 4

(A)

1. For which position of an object does a convex lens form a real and inverted image of the same size as that of object? Draw a labelled ray diagram to show the formation of the required image. [3 Marks]

Answer:
When the object is placed at twice the focal length (\( 2F_1 \)) in front of a convex lens, it forms a real, inverted image of the exact same size at \( 2F_2 \) on the other side.

[Figure: Ray diagram showing a convex lens with principal axis, optical centre O, principal foci F1, F2 and centers 2F1, 2F2. An object AB is placed at 2F1. A ray parallel to principal axis passes through F2, and another ray through optical centre O goes straight. They meet at 2F2 to form an inverted image A'B' of equal size.]

Teacher's Note:
a) This standard position (\( u = 2f \)) is often used in optical instruments to invert or transfer images without magnification.
b) All ray diagrams must include arrowheads on rays and labels for lens, object, image, and foci.

2. What is a galaxy? Name the different kinds of galaxies. [2 Marks]

Answer:
1. A galaxy is a vast, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter.
2. The different kinds of galaxies are spiral galaxies, elliptical galaxies, irregular galaxies, and starburst galaxies.

Teacher's Note:
a) Our solar system is located in the Milky Way, which is a spiral galaxy.
b) Mention classification names clearly to score full marks.

(B)

1. Identify the poles of the magnet in the figures (1) and (2) below: [2 Marks]

[Figure: Two bar magnets with magnetic field lines shown. Figure 1 shows field lines emerging from the left end and entering the right end. Figure 2 shows field lines entering the left end and emerging from the right end.]

Answer:
1. In Figure 1, the left pole is the North Pole (N) and the right pole is the South Pole (S) since magnetic field lines emerge from North and enter South outside the magnet.
2. In Figure 2, the left pole is the South Pole (S) and the right pole is the North Pole (N).

Teacher's Note:
a) Magnetic field lines always form closed continuous loops, running from North to South outside and South to North inside.
b) Direction arrows on field lines are crucial for identifying magnetic polarity.

2. Answer the following: [3 Marks]
(a) What is electromagnetic induction?
(b) In what way can the magnitude of the induced current be increased?

Answer:
(a) Electromagnetic Induction is the phenomenon of generating an electric current in a closed circuit due to a changing magnetic field linked with the coil.
(b) The magnitude of the induced current can be increased by:
1. Increasing the number of turns in the coil.
2. Increasing the strength of the magnetic field.
3. Increasing the relative speed of motion between the magnet and the coil.

Teacher's Note:
a) Discovered by Michael Faraday, this principle is the working basis of electric generators and transformers.
b) List all three factors clearly for full marks in descriptive sub-parts.

Question 5

(A)

1. Water wets the glass surface while mercury does not. Explain. [2 Marks]

Answer:
1. For water and glass, the adhesive force between water and glass molecules is greater than the cohesive force between water molecules. Hence, water wets glass.
2. For mercury and glass, the cohesive force between mercury molecules is much stronger than the adhesive force between mercury and glass. Hence, mercury does not wet glass.

Teacher's Note:
a) Adhesion is the attractive force between dissimilar molecules, while cohesion is between similar molecules.
b) This explains why water forms a concave meniscus while mercury forms a convex meniscus.

2. Give three differences between myopia and hypermetropia. [3 Marks]

Answer:

Teacher's Note:
a) Tabular format is best for "differences between" questions.
b) Ensure optical defect corrections are matched correctly with lens types.

(B)

1. What are the do's and dont's during a thunderstorm when you are outside the house? [3 Marks]

Answer:
The following precautions should be taken outside during a thunderstorm (Any three):
1. Do not carry an umbrella with a metallic rod over your head.
2. Do not stand near tall trees, electric poles, or high-rise metallic structures.
3. Take shelter around low-lying short trees or inside a building.
4. Do not lie flat on the ground; instead, squat low with hands on knees and head tucked between them.

Teacher's Note:
a) Tall isolated objects attract lightning due to high electric field concentration.
b) Squatting reduces body contact profile with the ground during step-potential hazards.

2. For what purposes is solar energy used? [2 Marks]

Answer:
Solar energy is used for various purposes, including:
1. Obtaining salt from sea water using shallow salt pans.
2. Drying agricultural crops and grains before storage.
3. Preserving various eatables and food items.
4. Heating water using solar water heaters and generating electricity via solar photovoltaic cells.

Teacher's Note:
a) Solar energy is a renewable, clean, and inexhaustible source of energy.
b) Mention at least two to four valid applications for full credit.

Question 6

(A)

1. Describe the advantages of high specific heat capacity of water as a coolant. [2 Marks]

Answer:
1. Water can absorb a large amount of heat energy with only a slight rise in its temperature due to its exceptionally high specific heat capacity.
2. This makes it an ideal and efficient coolant in industrial machinery and car radiators, as it can extract more heat from hot engine parts.

Teacher's Note:
a) The specific heat capacity of water is approximately \( 4200\text{ J kg}^{-1}\text{ K}^{-1} \).
b) Mention both high heat absorption capacity and temperature stability for full marks.

2. Answer the following: [3 Marks]
(a) What happens to the equivalent resistance and the current in a parallel circuit when more and more resistances are added?
(b) Name the physical quantity whose unit is volt/ampere.
(c) What is meant by potential difference between two points?

Answer:
(a) When more resistances are added in parallel, the total equivalent resistance decreases, which causes the total current drawn from the source to increase.
(b) Resistance (\( R = \frac{V}{I} \)).
(c) Potential difference between two points in an electric field is the amount of work done in moving a unit positive test charge from one point to the other.

Teacher's Note:
a) In parallel circuits, equivalent resistance is always less than the smallest individual resistor.
b) State units and definitions with precision according to Ohm's law.

(B)

1. Write a note on tides. [2 Marks]

Answer:
1. Tides are the periodic rise and fall of sea water levels occurring twice a day, caused mainly by the gravitational pull of the Moon and the Sun on Earth.
2. High tides help in clearing garbage near shores and can be harnessed to generate hydroelectric power.

Teacher's Note:
a) The time interval between two successive high tides is 12 hours and 24 minutes.
b) Spring tides occur during full moon and new moon when solar and lunar gravitational forces combine.

2. Ram throws a stone in the pond. It displaces 1.5 kg of water. Calculate the buoyant force acting on the stone (\( g = 9.8\text{ m/s}^2 \)). [3 Marks]

Answer:
Mass of water displaced (\( m \)) = \( 1.5\text{ kg} \)
Acceleration due to gravity (\( g \)) = \( 9.8\text{ m/s}^2 \)
Weight of displaced water = \( mg = 1.5 \times 9.8 = 14.7\text{ N} \)
According to Archimedes' Principle, Buoyant force = Weight of liquid displaced = \( 14.7\text{ N} \).

Teacher's Note:
a) State Archimedes' principle clearly in numerical problems involving upthrust.
b) Include correct SI units (\( \text{N} \) for force) in the final answer.

Question 7

(A)

1. 'A ray of light incident on a rectangular glass slab immersed in any medium emerges parallel to itself'. Draw a labelled ray diagram to justify the statement. [2 Marks]

Answer:
When a light ray passes through a parallel-sided glass slab, the extent of bending at the first surface equals the opposite bending at the second surface, making the emergent ray parallel to the incident ray with a lateral shift.

[Figure: Ray diagram of a rectangular glass slab PQRS showing an incident ray AO striking surface PQ at angle of incidence i, refracting along OB at angle r, and emerging along CD as emergent ray at angle e. Normals NN1 and MM1 are shown with lateral displacement.]

Teacher's Note:
a) The perpendicular distance between the incident ray and the emergent ray is called lateral displacement.
b) Ensure normals are drawn perpendicular to the slab boundaries.

2. State the rules for construction of ray diagrams for a convex lens along with the ray diagram. [3 Marks]

Answer:
The three principal rules for constructing ray diagrams for a convex lens are:
1. Rule 1: A ray of light incident parallel to the principal axis passes through the principal focus (\( F_2 \)) after refraction through the lens.
2. Rule 2: A ray passing through the optical centre (\( O \)) of the lens goes straight without any deviation.
3. Rule 3: A ray passing through the first principal focus (\( F_1 \)) becomes parallel to the principal axis after refraction.

[Figure: Three separate mini ray diagrams illustrating Rule 1 (parallel ray converging at focus), Rule 2 (ray through optical centre passing undeviated), and Rule 3 (ray through focus emerging parallel).]

Teacher's Note:
a) Any two rays are sufficient to locate the position of an image formed by a lens.
b) Label principal foci (\( F_1, F_2 \)) and optical centre (\( O \)) clearly in all ray sketches.

(B)

1. How much current will an electric bulb draw from a 220 V source, if the resistance of the filament of the bulb is \( 1200\text{ }\Omega \)? [2 Marks]

Answer:
Given: Voltage (\( V \)) = \( 220\text{ V} \), Resistance (\( R \)) = \( 1200\text{ }\Omega \)
From Ohm's law, current (\( I \)) is given by:
\( I = \frac{V}{R} \)
\( I = \frac{220}{1200} = 0.1833\text{ A} \) (or \( 0.18\text{ A} \)).

Teacher's Note:
a) Always state the given parameters and the formula before substituting values.
b) Express the final numerical answer with proper SI units (Ampere).

2. What is Pascal's law? Demonstrate it with the help of an experiment. [3 Marks]

Answer:
Pascal's Law states that pressure applied to an enclosed liquid is transmitted equally, undiminished in all directions.
Experiment:
1. Take a spherical glass flask with several small holes pierced all over its surface and fitted with a piston at its neck.
2. Fill the flask completely with water and push the piston inwards.
3. Water rushes out of all the holes simultaneously with equal force and velocity, demonstrating that liquid pressure is transmitted equally in all directions.

[Figure: Experimental setup showing a glass flask with a piston being pushed down, and water jets squirting out equally from multiple small holes around the bulb.]

Teacher's Note:
a) Pascal's law is the underlying principle behind hydraulic lifts, hydraulic brakes, and hydraulic presses.
b) Clearly mention both the definition statement and the experimental observation to earn full credit.