CUET UG Physics Booster Test 2- Rutherford Nuclear Model
📌 Answers are locked once submitted — results and explanations appear at the end.
QUESTION 1 OF 20
Alpha particle scattering confirms the planetary analogy.
Statements:
1. The massive central sun correlates with the atom's entire positive charge concentrated at the centre.
2. The sun's gravity is mathematically identical to the electrostatic force exerted by the nucleus.
3. The solar system has mostly empty space; similarly, electrons are at distances 10,000 to 100,000 times the nuclear size.
4. The planetary orbits are governed by electrostatic repulsion.
QUESTION 2 OF 20
Incorrect statement about the revolving planets analogy
QUESTION 3 OF 20
Correct statements about concentrated mass
1. The rebound of a small fraction of alpha particles indicates concentrated mass.
2. The target nucleus is assumed to remain stationary because it is heavily concentrated and about 50 times heavier than an alpha particle.
3. The nucleus occupies the entire atomic volume to provide the concentrated mass.
4. Most of the atom's mass tightly resides at its centre in a small volume.
QUESTION 4 OF 20
The large angle deflection of an alpha particle
QUESTION 5 OF 20
When computing the mathematical trajectory of an alpha particle scattered by a nucleus
QUESTION 6 OF 20
Match List I (Orbital concepts) with List II (Expressions/Dependencies)
| List I | List II |
|---|---|
| 1. Centripetal Force F꜀ | a. Inversely proportional to v² in stable orbit |
| 2. Orbit radius r | b. Has a negative sign indicating direction towards the origin |
| 3. Kinetic Energy K | c. Required to keep the electron in its stable orbit |
| 4. Potential Energy U | d. Equal to half the magnitude of the potential energy |
QUESTION 7 OF 20
The value of the scattering angle θ for a nearly undeviated particle (large impact parameter) will be approximately:
QUESTION 8 OF 20
For a beam of alpha particles traversing a thin gold foil, the distribution of impact parameters and the probabilities of different scattering directions are respectively:
QUESTION 9 OF 20
In the Geiger-Marsden experiment, out of 8,000,000 incident alpha particles, approximately how many particles are expected to deflect by more than 90°? (Assume 1 in 8000 deflect by more than 90°)
QUESTION 10 OF 20
In the case of a head-on rebound
QUESTION 11 OF 20
The initial kinetic energy of an incoming alpha particle
QUESTION 12 OF 20
During the scattering process, the final potential energy U of the system at the stopping point (distance d) is:
QUESTION 13 OF 20
Closest approach distance statements
1. It provides a reliable upper limit to the size of the target nucleus.
2. At this distance, kinetic energy is zero and electric potential energy is maximum.
3. It depends directly on the initial kinetic energy of the alpha particle.
4. It is exactly equal to the physical sum of the radii of the gold nucleus and the alpha particle.
QUESTION 14 OF 20
Incorrect statement about atomic dimensions
QUESTION 15 OF 20
In Rutherford's model, if the centripetal force was not continuously provided by the electrostatic attraction
QUESTION 16 OF 20
The orbital velocity v of the electron in a dynamically stable orbit of radius r in a hydrogen atom is given by
QUESTION 17 OF 20
For an orbiting electron in a hydrogen atom, the algebraic signs of its Kinetic Energy and Potential Energy are respectively:
QUESTION 18 OF 20
In terms of kinetic energy K, the potential energy U of an electron in a hydrogen atom is given by:
QUESTION 19 OF 20
If the total energy of an electron in a hydrogen atom is -2.2 × 10⁻¹⁸ J, what is the orbital radius?
(1 / 4πε₀ = 9.0 × 10⁹ N m²/C², e = 1.6 × 10⁻¹⁹ C)
QUESTION 20 OF 20
Correct statements about the bound state of an electron
1. The total energy of the electron is natively negative.
2. The electrostatic potential energy is strictly negative.
3. A positive total energy would mean the electron is unbound and does not follow a closed orbit.
4. The magnitude of the potential energy is exactly half the kinetic energy.
Test Complete!
Answer Review
1 Alpha particle scattering confirms the planetary analogy.
Statements:
1. The massive central sun correlates with the atom's entire positive charge concentrated at the centre.
2. The sun's gravity is mathematically identical to the electrostatic force exerted by the nucleus.
3. The solar system has mostly empty space; similarly, electrons are at distances 10,000 to 100,000 times the nuclear size.
4. The planetary orbits are governed by electrostatic repulsion.
�� Nucleus corresponds to the Sun. �� Most atomic volume is empty space. �� Gravity and electrostatic force are not identical.
Statement 1 is correct because Rutherford compared the nucleus to the central Sun containing most of the mass and positive charge. Statement 3 is correct because electrons are located at distances about 10⁴–10⁵ times the nuclear size, making the atom mostly empty space. Statements 2 and 4 are incorrect. Gravity and electrostatic force are different interactions, and planetary motion is not governed by electrostatic repulsion. Therefore, statements 1 and 3 are correct.
- �� Option B → Statements 2 and 4 are incorrect.
- �� Option C → Includes statement 2, which is incorrect.
- �� Option D → Includes statement 4, which is incorrect.
Used
- Elimination
Application:
- Identify valid features of the planetary analogy.
Final Logic:
- Only statements 1 and 3 correctly describe Rutherford's analogy.
Sun → Nucleus, Space → Atom
2 Incorrect statement about the revolving planets analogy
�� Nucleus dominates scattering. �� Electrons are very light. �� Electron fields produce negligible deflection.
The large-angle scattering observed by Rutherford is caused by the intense electric field of the positively charged nucleus, not by electrons. Electrons are too light to significantly alter alpha-particle trajectories. Therefore, option B is correct.
- �� Option A → Correct planetary analogy.
- �� Option C → Correct description of atomic emptiness.
- �� Option D → Correct explanation of electron negligibility.
Used
- Odd One Out
Application:
- Identify the statement inconsistent with Rutherford scattering.
Final Logic:
- Large deflections originate from the nucleus, not electrons.
Scatter → Nucleus, Not Electrons
3 Correct statements about concentrated mass
1. The rebound of a small fraction of alpha particles indicates concentrated mass.
2. The target nucleus is assumed to remain stationary because it is heavily concentrated and about 50 times heavier than an alpha particle.
3. The nucleus occupies the entire atomic volume to provide the concentrated mass.
4. Most of the atom's mass tightly resides at its centre in a small volume.
�� Backscattering indicates concentrated mass. �� Gold nucleus is much heavier. �� Mass is concentrated in a tiny nucleus.
Statements 1, 2 and 4 are correct. Large-angle scattering and rebound require a massive concentrated centre. The gold nucleus is treated as stationary because it is much heavier than the alpha particle. Most atomic mass is concentrated in the nucleus. Statement 3 is incorrect because the nucleus occupies only a tiny fraction of atomic volume.
- �� Option B → Includes statement 3.
- �� Option C → Includes statement 3.
- �� Option D → Includes statement 3.
Used
- Elimination
Application:
- Separate nuclear properties from atomic volume properties.
Final Logic:
- Mass is concentrated, but volume is not.
Tiny Volume, Huge Mass
4 The large angle deflection of an alpha particle
�� Large deflection needs strong repulsion. �� Strong field exists near nucleus. �� Supports nuclear model.
Large-angle scattering can occur only when the alpha particle approaches a highly concentrated positive charge. This produces a strong Coulomb repulsion and significant change in trajectory. Therefore, option B is correct.
- �� Option A → Alpha particles do not penetrate the nucleus.
- �� Option C → Rutherford assumed single scattering.
- �� Option D → Rutherford's results disproved the plum pudding model.
Used
- Contextual/Tonal Matching
Application:
- Relate scattering angle to electric field strength.
Final Logic:
- Strong nuclear field causes large deflections.
Large Deflection → Strong Nucleus
5 When computing the mathematical trajectory of an alpha particle scattered by a nucleus
�� Force must be known. �� Coulomb force causes scattering. �� Newton's law predicts motion.
The trajectory is calculated using Coulomb's law to determine the electrostatic repulsive force and Newton's second law to determine the resulting motion. Therefore, option C is correct.
- �� Option A → Force law is essential.
- �� Option B → Interaction is repulsive, not attractive.
- �� Option D → Coulomb force varies as 1/r².
Used
- Contextual/Tonal Matching
Application:
- Identify the laws used in Rutherford trajectory calculations.
Final Logic:
- Coulomb force + Newton's law determine motion.
Coulomb Gives Force, Newton Gives Motion
6 Match List I (Orbital concepts) with List II (Expressions/Dependencies)
| List I | List II |
|---|---|
| 1. Centripetal Force F꜀ | a. Inversely proportional to v² in stable orbit |
| 2. Orbit radius r | b. Has a negative sign indicating direction towards the origin |
| 3. Kinetic Energy K | c. Required to keep the electron in its stable orbit |
| 4. Potential Energy U | d. Equal to half the magnitude of the potential energy |
�� Centripetal force maintains orbit. �� Radius varies inversely with v². �� Potential energy is negative.
1 → c : Centripetal force keeps electron in orbit. 2 → a : r ∝ 1/v². 3 → d : K = |U|/2. 4 → b : Potential energy is negative. Therefore, option A is correct.
- �� Option B → Incorrect force and energy matching.
- �� Option C → Radius matched incorrectly.
- �� Option D → Centripetal force and kinetic energy mismatched.
Used
- Option Grouping
Application:
- Match orbital concepts with their physical properties.
Final Logic:
- Only option A correctly pairs all entries.
Force-Orbit, Radius-v², K-Half U
7 The value of the scattering angle θ for a nearly undeviated particle (large impact parameter) will be approximately:
�� Large impact parameter means distant encounter. �� Repulsion is weak. �� Deflection is negligible.
When the impact parameter is very large, the alpha particle remains far from the nucleus and experiences only a weak Coulomb force. Consequently, the scattering angle approaches zero. Therefore, option A is correct.
- �� Option B → Represents significant scattering.
- �� Option C → Represents backscattering.
- �� Option D → Physically not applicable here.
Used
- Contextual/Tonal Matching
Application:
- Relate impact parameter to scattering angle.
Final Logic:
- Large impact parameter gives θ ≈ 0.
Large b → Small θ
8 For a beam of alpha particles traversing a thin gold foil, the distribution of impact parameters and the probabilities of different scattering directions are respectively:
�� Different particles have different impact parameters. �� Different impact parameters give different angles. �� Probabilities therefore vary.
In a beam, particles approach nuclei with a range of impact parameters. This leads to a range of scattering angles and therefore different probabilities for different directions. Hence, option D is correct.
- �� Option A → Impact parameters are not constant.
- �� Option B → Impact parameters are not constant.
- �� Option C → Probabilities are not uniform.
Used
- Contextual/Tonal Matching
Application:
- Analyze beam statistics.
Final Logic:
- Different impact parameters produce different scattering probabilities.
Different b → Different θ
9 In the Geiger-Marsden experiment, out of 8,000,000 incident alpha particles, approximately how many particles are expected to deflect by more than 90°? (Assume 1 in 8000 deflect by more than 90°)
�� Probability = 1/8000. �� Total particles = 8,000,000. �� Multiply accordingly.
Number scattered by more than 90° = 8,000,000 × (1/8000) = 1000 Therefore, option C is correct.
- �� Option A → Incorrect calculation.
- �� Option B → Eight times larger than correct value.
- �� Option D → Far too small.
Used
- Substitution
Application:
- Multiply total particles by the given probability.
Final Logic:
- 8,000,000 ÷ 8000 = 1000.
8 Million ÷ 8000 = 1000
10 In the case of a head-on rebound
�� Head-on collision means minimum impact parameter. �� Maximum repulsion occurs. �� Particle reverses direction.
For a head-on collision, the impact parameter is minimum (ideally zero). The alpha particle approaches the nucleus, momentarily stops, and rebounds with a scattering angle approximately equal to π radians (180°). Therefore, option C is correct.
- �� Option A → Maximum impact parameter gives negligible scattering.
- �� Option B → Electrostatic force is strongest near closest approach.
- �� Option D → Alpha particles do not penetrate the nucleus in Rutherford's analysis.
Used
- Contextual/Tonal Matching
Application:
- Relate impact parameter to scattering outcome.
Final Logic:
- Minimum impact parameter gives backscattering.
Head-On → θ ≈ π
11 The initial kinetic energy of an incoming alpha particle
�� Closest approach depends on initial kinetic energy. �� Higher kinetic energy gives smaller closest approach distance. �� Energy conservation is used.
The distance of closest approach is obtained by equating the initial kinetic energy of the alpha particle to the electrostatic potential energy at the turning point: K = (1 / 4πε₀) × (2Ze² / d) Thus, the initial kinetic energy directly determines the value of d. Therefore, option B is correct.
- �� Option A → Kinetic energy decreases as the particle approaches the nucleus.
- �� Option C → Energy is converted into potential energy, not thermal heat.
- �� Option D → The kinetic energy originates from radioactive decay, not nuclear repulsion.
Used
- Contextual/Tonal Matching
Application:
- Relate closest approach to conservation of energy.
Final Logic:
- Initial kinetic energy fixes the turning point distance.
More KE → Smaller d
12 During the scattering process, the final potential energy U of the system at the stopping point (distance d) is:
�� Alpha particle charge = +2e. �� Gold nucleus charge = +Ze. �� Potential energy is positive because both charges are positive.
The electrostatic potential energy between two charges is: U = (1 / 4πε₀) × (q₁q₂ / d) Substituting: q₁ = +2e q₂ = +Ze Therefore, U = (1 / 4πε₀) × (2Ze² / d) Hence, option A is correct.
- �� Option B → Incorrect dependence on distance.
- �� Option C → Wrong sign; like charges give positive potential energy.
- �� Option D → Missing one factor of e.
Used
- Substitution
Application:
- Apply electrostatic potential energy formula.
Final Logic:
- U = (1 / 4πε₀)(2Ze² / d).
+2e × +Ze → Positive U
13 Closest approach distance statements
1. It provides a reliable upper limit to the size of the target nucleus.
2. At this distance, kinetic energy is zero and electric potential energy is maximum.
3. It depends directly on the initial kinetic energy of the alpha particle.
4. It is exactly equal to the physical sum of the radii of the gold nucleus and the alpha particle.
�� Closest approach estimates nuclear size. �� Turning point occurs when velocity becomes zero. �� Initial kinetic energy affects the distance.
Statements 1, 2 and 3 are correct. The distance of closest approach gives an upper limit to nuclear size. At this point the alpha particle momentarily stops, making kinetic energy zero and potential energy maximum. The value of d depends on the initial kinetic energy. Statement 4 is incorrect because d is generally much larger than the physical nuclear radius.
- �� Option B → Includes statement 4.
- �� Option C → Includes statement 4.
- �� Option D → Includes statement 4.
Used
- Elimination
Application:
- Identify the incorrect statement about closest approach.
Final Logic:
- Closest approach is not equal to physical nuclear contact.
d = Upper Limit, Not Radius
14 Incorrect statement about atomic dimensions
�� Closest approach exceeds nuclear radius. �� Nuclear radius is only a few femtometres. �� Atomic size is much larger.
For gold, the actual nuclear radius is approximately 6 fm (6 × 10⁻¹⁵ m), while the closest approach distance is roughly 30 fm (3 × 10⁻¹⁴ m). Thus, the distance of closest approach is larger, not smaller, than the nuclear radius. Therefore, option C is correct.
- �� Option A → Correct size ratio.
- �� Option B → Correct nuclear radius estimate.
- �� Option D → Correct implication of Rutherford's model.
Used
- Extreme Word Filter
Application:
- Compare actual nuclear radius with closest approach distance.
Final Logic:
- d > nuclear radius.
30 fm > 6 fm
15 In Rutherford's model, if the centripetal force was not continuously provided by the electrostatic attraction
�� Circular motion requires centripetal force. �� Electrostatic attraction supplies that force. �� Without it, closed orbits are impossible.
For an electron to move in a circular orbit, a centripetal force must continuously act toward the centre. In Rutherford's model, this force is provided by electrostatic attraction. Without this force, the electron cannot remain in a stable closed orbit. Therefore, option B is correct.
- �� Option A → Violates circular motion requirements.
- �� Option C → Unrelated to orbital dynamics.
- �� Option D → Not the direct consequence asked.
Used
- Contextual/Tonal Matching
Application:
- Apply the concept of centripetal force.
Final Logic:
- No centripetal force → No stable orbit.
Orbit Needs Centre Pull
16 The orbital velocity v of the electron in a dynamically stable orbit of radius r in a hydrogen atom is given by
�� Equate electrostatic and centripetal forces. �� Solve for v². �� Take square root.
Using: e² / (4πε₀r²) = mv² / r Therefore: v² = e² / (4πε₀mr) Hence: v = √[e² / (4πε₀mr)] Therefore, option A is correct.
- �� Option B → Missing square root.
- �� Option C → Incorrect factor of 2.
- �� Option D → Incorrect dimensions.
Used
- Substitution
Application:
- Use force balance equation.
Final Logic:
- Fₑ = F꜀ gives the orbital velocity.
Balance Forces → Get v
17 For an orbiting electron in a hydrogen atom, the algebraic signs of its Kinetic Energy and Potential Energy are respectively:
�� Kinetic energy is always positive. �� Attractive potential energy is negative. �� Bound systems have negative potential energy.
The kinetic energy of a moving electron is positive. The electrostatic potential energy of the electron-nucleus system is negative because the interaction is attractive. Therefore, option A is correct.
- �� Option B → Reverses the signs.
- �� Option C → Potential energy is not positive.
- �� Option D → Kinetic energy cannot be negative.
Used
- Odd One Out
Application:
- Recall signs of kinetic and potential energy.
Final Logic:
- K > 0 and U < 0.
Move → Positive K, Bind → Negative U
18 In terms of kinetic energy K, the potential energy U of an electron in a hydrogen atom is given by:
�� Coulomb orbit relation. �� Potential energy is twice kinetic energy in magnitude. �� Sign is negative.
For a hydrogen atom: K = e² / (8πε₀r) U = -e² / (4πε₀r) Therefore: U = -2K Hence, option D is correct.
- �� Option A → Incorrect factor and sign.
- �� Option B → Wrong sign.
- �� Option C → Incorrect factor.
Used
- Substitution
Application:
- Compare standard energy expressions.
Final Logic:
- Potential energy equals minus twice kinetic energy.
U = -2K
19 If the total energy of an electron in a hydrogen atom is -2.2 × 10⁻¹⁸ J, what is the orbital radius?
(1 / 4πε₀ = 9.0 × 10⁹ N m²/C², e = 1.6 × 10⁻¹⁹ C)
�� Use total energy formula. �� E = -e² / (8πε₀r). �� Solve for r.
For hydrogen: E = -e² / (8πε₀r) Therefore: r = e² / (8πε₀|E|) Substituting values: r = (9 × 10⁹)(1.6 × 10⁻¹⁹)² / [2(2.2 × 10⁻¹⁸)] r ≈ 5.3 × 10⁻¹¹ m Therefore, option A is correct.
- �� Option B → Far too large.
- �� Option C → Nuclear scale, not orbital scale.
- �� Option D → Incorrect numerical result.
Used
- Substitution
Application:
- Use the total energy equation directly.
Final Logic:
- The calculation gives the Bohr radius value.
Ground State → 5.3 × 10⁻¹¹ m
20 Correct statements about the bound state of an electron
1. The total energy of the electron is natively negative.
2. The electrostatic potential energy is strictly negative.
3. A positive total energy would mean the electron is unbound and does not follow a closed orbit.
4. The magnitude of the potential energy is exactly half the kinetic energy.
�� Bound electrons have negative total energy. �� Potential energy is negative. �� Positive total energy means escape.
Statements 1, 2 and 3 are correct. For a bound electron: E < 0 U < 0 Positive total energy implies an unbound state. Statement 4 is incorrect because: |U| = 2K not |U| = K/2 Therefore, option A is correct.
- �� Option B → Includes statement 4.
- �� Option C → Includes statement 4.
- �� Option D → Includes statement 4.
Used
- Elimination
Application:
- Use standard hydrogen atom energy relations.
Final Logic:
- Bound state requires E < 0 and U = -2K.
Bound → E Negative, U = -2K
