ICSE Physics Competency Based Questions Solution- Multiple Choice Questions

ICSE Physics Competency Based Questions Solution:

I. Multiple Choice Questions

Question 1. [Light]
When light enters from air to glass, it bends toward the normal. If red, blue, and yellow colours are allowed to enter the same glass block at the same angle of incidence, then for which colour, the value of ∠𝑖 − ∠𝑟, be greater?
(a) green
(b) red
(c) blue
(d) yellow

Answer: (c) blue

Explanation: When light enters from rarer to denser medium, it bends towards normal. The colour with least speed deviates the most. Looking at the spectrum VIBGYOR, Blue light, among the given 4 colours above, deviates the most. Hence, ∠𝑖 − ∠𝑟 will be greatest in blue colour.

Question 2. [Light]
Assertion (A): When light passes through a triangular prism, it is observed that for two angles of incidence, the angle of deviation is the same.
Reason (R): According to the principle of reversibility, the light retraces the path in reversing the direction.
(a) A and R are true, and R is the reason for A.
(b) A and R are true, and R is not the reason for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (a) A and R are true and R is the reason of A.

Explanation: When light enters a triangular prism from one surface, the angle of incidence is i₁ , and when it emerges from the other surface of the prism, the angle of emergence is i₂ . i₂ becomes angle of incidence and i₁ becomes angle of incidence when the light reverse its path. Thus for both the angle of incidences angle of deviation would be same, as angle of deviation (D)= i₁+ i₂ -A.

Question 3. [Light]
Which of the following diagrams shows the correct path of light through the lens?

Answer:

Explanation: Concave lens diverges the ray after refraction.

Question 4. [Force, Work, Power and Energy]
The diagrams below show four pulley systems. State which of the statements following the diagrams is true.

(a) There are three pulley systems with V.R. = 2 and one pulley system with V.R. = 1.
(b) There are two pulley systems with V.R. = 2, one pulley system with V.R. = 3 and one
pulley system with V.R. = 1.
(c) There are two pulley systems with V.R. = 2, one pulley system with V.R.= 3 and one
pulley system with V.R. = 4.
(d) There are two pulley systems with V.R. = 2 and two pulley system with V.R. = 3.

Answer: (d) There are two pulley systems with V.R. = 2 and two pulley system with V.R. = 3

Explanation: Both pulleys on the right have V.R-2 , due to the movable pulleys The top left one has V.R-3 , as it has three distinguishable strands lifting the Load. The bottom left one has V.R-3 using the same method as the top left one.

Question 5. [Force, Work, Power and Energy]
The diagrams below show a force F = 40 N acting on a rod AB pivoted at A in different directions. Identify the correct statement.

(a) P and S have opposite moments.
(b) The magnitude of the moment of force is maximum in R.
(c) The magnitude of the moment of force is maximum in P and Q.
(d) The moment of force in R is negative.

Answer: (c) The magnitude of the moment of force is maximum in P and Q.

Explanation: Moment of force is calculated as the product of force and the perpendicular distance from the pivot point to the line of action of the force.

Question 6. [Force, Work, Power and Energy]
In the diagram below, four cones are depicted, each with a height of 12cm. The position of the center of gravity is indicated by dots located at 9cm, 8cm, 4cm, and 3cm from the apex of each cone. Which of these cones is completely solid?

(a) 9cm
(b) 8cm
(c) 4cm
(d) 3cm

Answer: (a) 9cm

Explanation: C.G. of a solid cone is 3h/4 from the apex.

Question 7. [Force, Work, Power and Energy]
The given figure depicts the graph of work done vs. displacement under a constant force of 10N. Which of the following statements is true?

(a) Force is acting at an angle of 0^o with the displacement.
(b) Force is acting at an angle of 45^o with the displacement.
(c) Force is acting at an angle of 60^o with the displacement.
(d) Force is acting at an angle of 90^o with the displacement.

Answer: (c) Force is acting at an angle of 60° with the displacement.

Explanation: We know, W = F . S cosθ

50 = 10 x 10 cosθ

50/100 = cosθ

1/2 = cosθ

cos 60° = cos θ

Hence angle is 60°

Question 8. [Force, Work, Power and Energy]
During his experiments with a single movable pulley, Jas determined the effort, mechanical advantage and efficiency as X, Y & Z, respectively. Subsequently, after lubricating the pulley thoroughly, he recalculated the effort, MA and efficiency. X’, Y’ & Z’ respectively. Which of the following relationships accurately represents the scenario?
(a) X’ > X
(b) Y’ < Y

Answer: (c) Z’> Z

Explanation: After lubrication, effort will decrease and MA and efficiency will increase.

Question 9. [Light]
Assertion: For a glass block, the i vs. r graph is a straight line.
Reason: When a ray of light undergoes refraction, it follows Snell’s law.
(a) Both Assertion and Reason are true, and the Reason is the correct explanation of the
Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of the
Assertion.
(c) Assertion is true, but the Reason is false.
(d) Assertion is false, but the Reason is true.

Answer: (d) Assertion is false, but the Reason is true.

Explanation: The assertion is false because the i vs r graph for a glass block is not a straight line.

Question 10. [Sound]
___________________ of UV > _____________________ of microwaves
The quantity suitable for filling in both the blanks is:
(a) speed in vacuum
(b) speed in a medium
(c) frequency
(d) wavelength.

Answer: (c) frequency

Explanation: The wavelength and frequency are inversely proportional. Wavelength of UV is less than microwave. Hence, frequency of UV is greater than microwave.

Question 11. [Sound]
Sumit, a teenager, enjoys playing his music loudly. However, his grandmother consistently lowers the volume of the music player. Analyse the wave to identify which characteristic of the wave has been altered when the grandmother reduces the volume.

(a) The length PS becomes more.
(b) The length SR becomes less.
(c) The length QR becomes less.
(d) The length PR becomes less.

Answer: (c) The length QR becomes less.

Explanation: QR is the amplitude of sound wave. Greater the amplitude, louder the sound.

Question 12. [Heat]
Data: mass =10g quantity of heat supplied =120J rise in temperature = 100 °C
STATEMENT A: The heat capacity of the substance is 12 J/g.
STATEMENT B: The specific heat capacity of the substance is 1.2 J/gK.
(a) Only statement A is correct.
(b) Only statement B is correct.
(c) Both statements A and B are correct.
(d) Both statements A and B are incorrect.

Answer: (b) Only statement B is correct.

Explanation: Specific heat capacity (c) = H/mx ΔT

c = 120/1000 = 0.12 J/gK

Heat capacity (c’) = m x c

= 10 x 0.12 = 1.2 J/g

Question 13. [Electricity and Magnetism]
Given that the resistivity of Gold and Platinum is 2.1×10^-8 and 10.5×10^-8 ohm m, respectively, which is the correct statement?
STATEMENT A: 5 metres of platinum wire will have the same resistance as one metre of gold wire.
STATEMENT B: Gold wire of 1cm radius will have the same resistance as platinum wire of 5cm radius.
(a) Only statement A is correct.
(b) Only statement B is correct.
(c) Both statements A and B are correct.
(d) Both statements A and B are incorrect.

Answer: (d) Both statements A and B are incorrect.

Explanation:

\[For\;statement\;A,\;\\Let\;R_{1\;}and\;R_2\;be\;the\;resis\tan ces\;of\;gold\;and\;platinum\;wires\\and\;their\;cross\;sectional\;areas\;be\;same.\\R_1\;=\rho.\frac la\\\;=2.1×10^{-8}\times\frac1a\\R_1\;=\;\frac{2.1×10^{-8}}a\\R_2\;=10.5×10^{-8}\times\;\frac5a\\\;=\;\frac{52.5×10^{-8}}a\\\therefore R_1\neq R_2\\For\;statement\;B,\\Let\;their\;lengths\;be\;same.\\R_1=\rho.\frac la\\\;=2.1×10^{-8}\times\frac l{\mathrm\pi{(0.01)}^2}\\\;=2.1×10^{-8}\times\frac{10000}{\mathrm\pi}\\\;=\frac{2.1×10^{-8}\times10^4}{\mathrm\pi}\\\;=\frac{2.1×10^{-4}}{\mathrm\pi}\\R_2=10.5×10^{-8}\times\frac l{\mathrm\pi{(0.05)}^2}\\\;=10.5×10^{-8}\times\frac{10000}{25\mathrm\pi}\\\;=\frac{10.5×10^{-8}\times4\times10^2}{\mathrm\pi}\\\;=\frac{42\times10^{-6}}{\mathrm\pi}\\\therefore R_1\neq R_2\\Hence\;both\;the\;statements\;A\;and\;B\;are\;incorrect.\\\;\]

Question 14. [Electricity and Magnetism]
Assertion: A switch will serve the purpose of making and breaking a circuit when it is connected to the neutral wire.
Reason: Neutral wire is at zero potential.
(a) Both Assertion and Reason are true, and the Reason is the correct explanation of the Assertion
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of the Assertion
(c) Assertion is true, but the Reason is false.
(d) Both Assertion & Reason are false.

Answer: (b) Both Assertion and Reason are true, but Reason is not the correct explanation of the
Assertion.

Explanation: A switch controls the flow of current in a circuit by creating or breaking the connection. It doesn’t matter if it’s connected to the neutral or live wire; the key is completing or interrupting the circuit. The working of switch is not dependent on the potential of Neutral wire.

Question 15. [Electricity and Magnetism]
The given rods will attract each other when:

(a) A and C are connected to positive terminal of the battery.
(b) B and C are connected to the positive terminal of the battery.
(c) A and D are connected to the positive terminal of the battery.
(d) A and D are connected to the negative terminal of the battery.

Answer: (a) A and C are connected to the positive terminal of the battery.

Explanation: When A is connected to positive terminal of the battery, the current will flow in anticlockwise direction at the face near to the other iron bar. Thus, the face closer to the other bar will become north pole.

When A is connected to positive terminal of the battery, the current will flow in clockwise direction at the face near to the other iron bar. Thus, the face closer to the other bar will become south pole. Hence, both the bars will attract each other.

Question 16. [Modern Physics]
Which of the following equations are correctly balanced?

(a) Only D
(b) Only C
(c) Both A & B
(d) Both C & D

Answer: (d) Both C & D

Explanation: In equation C, when one He or alpha particle is emitted, mass number is reduced by 4 and atomic number by 2. Thus, mass number will be q-1-4= -5 and atomic number will be p-5-2= p-7.

In equation D, when two e or beta particles are emitted, mass number remains the same and atomic number is increased by 2. Thus, mass number will be q-4 and atomic number will be p-7+2= p-5.

Question 17. [Sound]
The above picture shows three cylinders filled with water to a different extent. The tuning forks L, M and N in vibration produce louder sound when held above the mouth of the cylinders. Which combination is correct for hearing a louder sound of the tuning fork?

(a) L – R, M – Q, N – P
(b) L – P, M – Q, N – R
(c) L – R, M – P, N – Q
(d) L – Q, M – R, N – P

Answer: (d) L– Q, M – R, N – P

Explanation: longer the tuning fork, less is the frequency and the longer the length of a vibrating air column, the smaller the pitch of the sound produced. Hence, perfect combination will be L – Q, M – R, N – P.

Question 18. [Heat]
Three metals, A, B and C, are supplied with the same quantity of heat. Their masses are in the ratio 2 : 3 : 4. If they show the same rise in the temperature, then the ratio of their thermal capacities will be:
(a) 1 : 1 : 1
(b) 4 : 3 : 2
(c) 2 : 3 : 4
(d) 2 : 3 : 1

Answer: (a) 1:1:1

Explanation: Let the masses of A , B and C be 2x, 3x and 4x respectively and their specific heat capacities be A_c, B_c and C_c respectively.

Given that Heat supplied(H) is same and rise in temperature(T) are same.

Hence H_A = H_B = H_C

2xA_cT = 3xB_cT = 4xC_cT

2A_c =3B_c = 4C_c

Hence thermal capacities are equal. [as mass x sp. heat capacity = thermal capacity]

Question 19. [Electricity and Magnetism]

The above diagram shows different copper conductors of diameters d and 2d and lengths, which are multiples of l. The increasing order of their resistances will be:
(a) A < B < C < D
(b) A < C < D < B
(c) A < D < C < B
(d) D < A < C < B

Answer: (b) A< C < D < B

Explanation: Resistance increases with increase in length and decreases with increase in cross-sectional area.

Question 20. [Sound]

The diagram shows the magnificent dome at Gol Ghumbaz at Bijapur. A boy standing at A whispers, and it is clearly heard at B across the huge dome. [Speed of sound is 330 ms^-1]
Assertion (A): The distance travelled by sound waves (x+y) should be < 33 m.
Reason (R): Sound reflected within 0.1 s is not heard by humans.
(a) A and R are true, and R is the reason for A.
(b) A and R are true, and R is not the reason for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (d) A is false, but R is true.

Explanation: o hear an echo the minimum distance between the source of sound and reflector should be 17 m.

Question 21. [Electricity and Magnetism]
A magnetic compass is present on a small table, very close to the wall in a room. A man enters the room and switches on the Air Conditioner fitted near the ceiling. He observes that the needle in the compass shows immediate deflection. Identify the most probable reason for the deflection.
(a) Air blowing in the room.
(b) Current starts flowing through AC wire concealed in the adjacent wall.
(c) Vibrations are produced when the Man starts talking to his wife in the kitchen.
(d) Vibrations were produced due to a file in his hand that fell on the ground.

Answer: (b) Current starts flowing through AC wire concealed in the adjacent wall.

Explanation: According to magnetic effect of current, when current flows through a conducting wire, a magnetic field is created around it.

Question 22. [Heat]
Two substances, A and B, have the same mass. Substance A has a higher specific heat capacity than substance B. What consequences would you expect when these substances are subjected to the same amount of heat energy?
(a) Substance A will experience a smaller temperature change than substance B.
(b) Substance A will experience a larger temperature change than substance B.
(c) Both substances will experience the same temperature change.
(d) Either of them can show a greater change in temperature as the temperature change depends on factors other than specific heat capacity.

Answer: (a) Substance A will experience a smaller temperature change than substance B.

Explanation: Heat energy = mass x sp. heat capacity x change in temperature. If heat energy supplied and masses of both A and B are same and specific heat capacity of A is higher then B then, A will experience a larger temperature change than B.

Question 23. [Light]
A student traces the path of a ray of light through a glass prism for different angles of incidence. He analyses each diagram and draws the following conclusion:
I. On entering the prism, the light ray bends towards its base.
II. Light ray suffers refraction at the point of incidence and at the point of emergence while passing through the prism.
III. An emergent ray bends at a certain angle to the direction of the incident ray.
IV. While emerging from the prism at the second surface, the angle of refraction is less than the angle of incidence at that surface.
Which of the above inferences are correct?
(a) I, II and III
(b) I, III and IV
(c) II, III and IV
(d) All of these.

Answer: (a) I, II and III

Explanation: When light ray emerges from the prism, it travels from denser to rarer medium. According to the rule of refraction, it will bend away from the normal. Hence, angle of refraction will be more than angle of incidence at that surface.

Question 24. [Force, Work, Power and Energy]
A metal ball is whirled inside a ring placed on a table, as shown in the diagram P. The diagram Q shows the motion of the ball after the ring is lifted.

Which of the following diagrams shows the correct position of the metal ball in the ring when the ring is lifted?

Answer: (c)

Explanation: Initially the ball was moving in a circular motion because of the influence of centripetal force on it. As soon as the ring is lifted, the centripetal force ceases to act and the ball will move tangentially to its position on the circular path. Here the diagram Q shows its motion after the ring is lifted. The direction is forward. The position initial it in circular motion will be diagram (c).

Question 25. [Light]
Assertion (A): Sometimes the sky appears reddish in the evening.
Reason (R): Red, being longer in wavelength, scatter more than the other colours.
(a) A and R are true, and R is the reason for A.
(b) A and R are true, and R is not the reason for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (c) A is true, but R is false.

Explanation: The wavelength of Red is longer than the other colour rays in the visible spectrum. Hence, it scatters the least and reaches our eyes but others do not.

Question 26. [Force, Work, Power and Energy]
Assertion (A): When the displacement is zero, then the work is zero. So, if the work done is zero, then it necessarily means the displacement is zero.
Reason (R): Work done is calculated by the relation 𝑊 = 𝐹𝑆𝑐𝑜𝑠𝜃
(a) A and R are true, and R is the reason for A.
(b) A and R are true, and R is not the reason for A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Answer: (d) A is false, but R is true.

Explanation: If the work done is zero, then it doesn’t necessarily means that the displacement is also zero. If the displacement is normal to the direction of force, then also work done is zero.

Question 27. [Force, Work, Power and Energy]
Which of the following statement is CORRECT?
The frequency of a stretched string is:
(a) directly proportional to its length but inversely proportional to the tension of the
wire.
(b) inversely proportional to its length but directly proportional to the tension of the
wire.
(c) directly proportional to the square root of its length but inversely proportional to the
tension of the wire.
(d) inversely proportional to its length but directly proportional to the square root of the
tension of the wire.

Answer: (d) inversely proportional to its length but directly proportional to the square root of the
tension of the wire.

Explanation: This means that a longer string will vibrate at a lower frequency, and a string with higher tension will vibrate at a higher frequency.

Question 28. [Light]
A ray of light passes obliquely from an optical medium of refractive index 1.33 to another medium of refractive index 1.5. While passing from the first medium to the second, the light ray will:
(a) bend towards the normal.
(b) bend away from the normal.
(c) move along the normal.
(d) suffer total internal reflection.

Answer: (a) Bend towards the normal.

Explanation: Refractive index of optically denser medium is always more than the rarer medium. As light is travelling from rarer to denser medium, it will bend towards the normal.

Question 29. [Light]
You want to register your name for an examination. For registration purposes, you need a passport-size photograph of yourself. When you went to a studio, the photographer told you to sit on a chair in front of a white screen in the room.

Assertion (A): This is purposefully done so that you as an object should stand beyond the centre of curvature of the camera lens, but surely not at an infinite distance.
Reason (R): The characteristics of the image formed are that it can be taken on a screen and is also diminished in size.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, and R is not the correct explanation of A.
(c) A is true, but R is false.
(d) Both A and R are false.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

Explanation: Camera lens is convex lens. An object situated beyond centre of curvature in front of a convex lens will produce a real, inverted image which is smaller than the size of the object.

Question 30. [Heat]
Rivers which originate from the glaciers at high altitudes have a supply of water throughout the year. This is because ice in high mountains does not melt all at once. This is due to:
(a) high specific heat of ice.
(b) low specific heat of ice.
(c) low specific latent heat of fusion of ice.
(d) high specific latent heat of fusion of ice.

Answer: (d) High specific latent heat of fusion of ice.

Explanation: Ice has high specific latent heat of fusion. That means, it requires a lot of heat to melt.

Question 31. [Electricity and Magnetism]
If three resistors 𝑅₁, 𝑅₂ and 𝑅₃ are connected in series and by R₁ ˃ R₂ ˃ R₃, then what is the relation between the currents 𝐼₁, 𝐼₂ and 𝐼₃ respectively flowing through them?
(a) 𝐼₁ = 𝐼₂ = 𝐼₃
(b 𝐼₁ < 𝐼₂ < 𝐼₃
(c) 𝐼₁ > 𝐼₂ > 𝐼₃
(d) 1/𝐼₁ < 1/ 𝐼₂ < 1/𝐼₃

Answer: (a) I₁ = l₂ = I₃

Explanation: When resistors are connected in series, same amount of current flows through each one of them.

Question 32. [Sound]

What is the ratio of wavelengths between P, Q and R?
(a) 3 : 2 : 1
(b) 1 : 2 : 3
(c) 6 : 3 : 2
(d) 2 : 3 : 6

Answer: (d) 2 : 3 : 6

Explanation: Wavelength is inversely proportional to frequency.

\[f_{P\;}:\;f_Q:\;f_R=3\;:\;2\;:\;1\\\therefore\curlywedge_{P\;\;}:\;\curlywedge_Q\;:\curlywedge_R=\frac13\;:\;\frac12\;:\;1\\\;\;=\;\frac13\times6\;:\;\frac12\times6\;:\;1\times6\\\;\;=\;2\;:\;3\;:\;6\]

Question 33. [Heat]
During the change of state of a substance from solid to liquid, heat is absorbed by a body, but its temperature does not rise. Which of the following statements explains the phenomenon?
(a) Only K.E of the molecules increases, but P.E remains the same.
(b) Only P.E of the molecules increases, but K.E remains the same.
(c) Both K.E and P.E of the molecules increase.
(d) There is no increase in the P.E and K.E of the molecules.

Answer: (b) Only the P.E of the molecules increases, but the K.E remains the same.

Explanation: K.E. is directly proportional to temperature. If temperature does not rise K.E. will also not rise. But the body is absorbing heat, so the intermolecular distance increases and thus, the P.E. increases.

Question 34. [Electricity and Magnetism]
Assertion (A): When current is passed through a wire, a magnetic field is generated around the wire.
Reasoning (R): Whenever there is a change of magnetic flux linked up with the coil, the induced current is generated in the coil.
(a) Both A and R are correct, and R is the correct explanation of A.
(b) Both A and R are correct, but R is not the correct explanation of A.
(c) A is correct but R is wrong.
(d) Both A and R are wrong.

Answer: (b) Both A and R are correct, but R is not the correct explanation of A.

Explanation: The Reason explains the phenomenon of magnetic induction.

Question 35. [Modern Physics]
Which of the following combinations correctly shows the charges on the particles?

1.6 X 10^-19 C -1.6 X 10^-19 C + 3.2 X 10^-19 C
(a) proton neutron alpha particle
(b) alpha particle electron neutron
(c) proton electron alpha particle
(d) electron Proton alpha particle

Answer: (c) proton electron alpha particle.

Explanation: Proton and electron have equal but opposite charges. Proton have positive and electron have negative charge. Charge on an alpha particle is equal to that of 2 protons.