Q.10 Physics · Section A ⭐ 360° Option Elimination Active

NEET 2024 Physics Question 10 Solution

Topic: Dual Nature of Radiation and Matter · Official NTA Booklet Code T1

Question

If c is the velocity of light in free space, the correct statements about photon among the following are: A. The energy of a photon is E = hν. B. The velocity of a photon is c. C. The momentum of a photon, p = hν/c. D. In a photon-electron collision, both total energy and total momentum are conserved. E. Photon possesses positive charge. Choose the correct answer from the options given below:

✓

Verified Against NTA Final Answer Key

Option (4) : A, B, C and D only

📚 Dual Nature of Radiation and Matter Easy

📋 Given Parameters & Problem Setup

Statement A The energy of a photon is E = hν.

Statement B The velocity of a photon is c.

Statement C The momentum of a photon, p = hν/c.

Statement D In a photon-electron collision, both total energy and total momentum are conserved.

Statement E Photon possesses positive charge.

⚡

The 30-Second Exam Hall Shortcut: ⚡ Neutral Photon Elimination Hack

⏱️ Save ~40 seconds

Photons are electrically neutral (zero charge) -> Statement E is completely FALSE -> Eliminate all options containing E!

1 Photons are neutral quanta of radiation: Charge = 0. Thus, Statement E ("Photon possesses positive charge") is completely FALSE.

2 Check options: Option (2) contains E -> Eliminate!

3 Check Statements A, B, C, D:

4 - A: E = hν (Planck’s quantum hypothesis -> True).

5 - B: Speed in free space = c (Universal constant -> True).

6 - C: Momentum p = E/c = hν/c (de Broglie / Einstein relation -> True).

7 - D: In photon-electron collision (Compton scattering), total energy and momentum are conserved (Elastic collision -> True).

8 Statements A, B, C and D are all correct -> Option (4) is the exact match!

🛡️

Why You Can 100% Trust This Shortcut: Einstein’s Photon Picture of Electromagnetic Radiation (Photons are electrically neutral quanta with energy E = hν and momentum p = hν/c).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Verification of Statement A (Photon Energy)

According to Planck’s quantum hypothesis as formulated by Einstein, electromagnetic radiation is emitted and absorbed in discrete packets called quanta or photons. The energy of a photon of frequency ν is given by:

E = h\nu = \frac{hc}{\lambda} \quad (\text{Statement A is True})

Step 2

Verification of Statement B (Photon Velocity)

In free space (vacuum), all photons, irrespective of their frequency or wavelength, travel at the universal constant speed of light c = 3 × 10⁸ m/s:

v = c \quad (\text{Statement B is True})

Step 3

Verification of Statement C (Photon Momentum)

From relativistic kinematics and the de Broglie relation, the momentum p of a photon is related to its energy E by p = E/c:

p = \frac{E}{c} = \frac{h\nu}{c} = \frac{h}{\lambda} \quad (\text{Statement C is True})

Step 4

Verification of Statement D (Collision Conservation Laws)

In particle-like collisions such as photon-electron collisions (e.g. Compton scattering), the interaction is perfectly elastic, meaning both total energy and total momentum are conserved:

\sum E_i = \sum E_f, \quad \sum \vec{p}_i = \sum \vec{p}_f \quad (\text{Statement D is True})

Step 5

Verification of Statement E (Charge of Photon)

Photons are electrically neutral. They are not deflected by electric or magnetic fields and possess zero rest mass and zero electrical charge:

q_{photon} = 0 \ne +e \quad (\text{Statement E is False})

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 (1)

✗ Incorrect

Verdict & Scientific Reason:

Incomplete; Statement B is also universally true.

⚠️

Student Fallacy (Why candidates pick this trap): Uncertain whether photon velocity in vacuum is always c.

2 (2)

✗ Incorrect

Verdict & Scientific Reason:

Contains Statement E, which is completely false.

⚠️

Student Fallacy (Why candidates pick this trap): Confusing photons with positively charged positrons or protons.

3 (3)

✗ Incorrect

Verdict & Scientific Reason:

Omit C and D, both of which are valid physical properties.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking photons do not carry momentum because they have zero rest mass.

4 (4)

✓ 100% Correct

Verdict & Scientific Reason:

All four statements A, B, C, and D are canon properties; E is false.

💡

Why this is airtight: None.

⚠️

NTA Trap Alert: Photon Neutrality vs Proton Confusion

Under exam pressure, students sometimes confuse "photon" with "proton" and think it carries a positive charge.

🛡️ How to avoid the -1 mark: Always emphasize: Photon = Light packet (zero charge). Proton = Nuclear particle (+1.6 × 10⁻¹⁹ C).

📖

Core NEET Syllabus Standard

Physics Core Modern Physics · Dual Nature of Radiation and Matter Standard Benchmark

Core Scientific Principle Tested:

"Photons are electrically neutral packets of electromagnetic energy traveling at speed c, possessing energy E = hν, momentum p = hν/c, and exhibiting elastic particle collisions."

Syllabus Focus: Photon Picture of Electromagnetic Radiation

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Photons are Neutral (No Charge at all): E is OUT, A-B-C-D standing TALL!

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NEET 2024 Physics Question 10 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Neutral Photon Elimination Hack

Step-by-Step Rigorous Workflow & Mathematical Proof

Verification of Statement A (Photon Energy)

Verification of Statement B (Photon Velocity)

Verification of Statement C (Photon Momentum)

Verification of Statement D (Collision Conservation Laws)

Verification of Statement E (Charge of Photon)

360° Option Elimination Engine Key Feature

NTA Trap Alert: Photon Neutrality vs Proton Confusion

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

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