IIT JEE Physics Dual Nature and Atoms MCQs with answers, explanations, and instant scoring.

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1. Photoelectric effect proves:

Particle nature of light
Wave nature
Nuclear nature
None

2. Einstein photoelectric equation is:

\(hf = KE + \phi\)
\(E=mc^2\)
\(V=IR\)
None

3. Work function depends on:

Material
Frequency
Intensity
None

4. De Broglie wavelength is:

\(h/p\)
\(p/h\)
\(hf\)
None

5. Photon energy is:

\(hf\)
\(h/f\)
\(p/h\)
None

6. Davisson-Germer experiment proves:

Wave nature of electron
Particle nature
Nuclear force
None

7. Bohr radius depends on:

\(n^2\)
n
1/n
None

8. Energy levels are:

Discrete
Continuous
Random
None

9. Ionization energy means:

Remove electron
Add electron
Move electron
None

10. Spectral lines arise due to:

Electron transition
Motion
Collision
None

11. Photon momentum:

\(h/\lambda\)
\(hv\)
\(h\lambda\)
None

12. Threshold frequency:

Minimum frequency
Maximum
Zero
None

13. KE max formula:

\(hf-\phi\)
\(hf+\phi\)
\(\phi-hf\)
None

14. Electron charge:

-1.6×10⁻¹⁹ C
+1.6×10⁻¹⁹ C
0
None

15. Electron mass:

9.1×10⁻³¹ kg
10⁻²⁷
10⁻²³
None

16. Energy level depends on:

n
mass
charge
None

17. Hydrogen spectrum is:

Line
Continuous
None
Zero

18. Energy transition emits:

Photon
Electron
Proton
None

19. Frequency relation:

ΔE/h
h/ΔE
none
zero

20. De Broglie applies to:

All particles
Only photons
None
Zero

21. Photon has:

Zero rest mass
Mass
Charge
None

22. Speed of photon:

c
v
none
zero

23. Photoelectric current depends on:

Intensity
Frequency
None
Zero

24. Stopping potential depends on:

Frequency
Intensity
None
Zero

25. Planck constant unit:

J·s
J
s
None

26. Bohr model uses:

Quantized orbits
Random orbits
None
Zero

27. Energy quantization means:

Discrete
Continuous
None
Zero

28. Electron transition upward means:

Absorption
Emission
None
Zero

29. Electron transition downward means:

Emission
Absorption
None
Zero

30. Ionization energy of H:

13.6 eV
10 eV
5 eV
None

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IIT JEE Physics Notes – Dual Nature of Matter & Radiation + Atoms (Set 14)

This is one of the most important and highest-scoring sections in IIT JEE Physics. Questions are generally direct, conceptual, and formula-based, especially from photoelectric effect and Bohr’s model. With clear concepts, you can easily score full marks.

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PART 1: DUAL NATURE OF RADIATION & MATTER

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1. Dual Nature of Light

Light exhibits:

• Wave nature → Interference, diffraction
• Particle nature → Photoelectric effect

👉 This leads to the concept of wave-particle duality.

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2. Photoelectric Effect

When light falls on a metal surface, electrons are emitted.

Key Observations:

• Emission is instantaneous
• Depends on frequency, not intensity
• No emission below threshold frequency

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3. Einstein’s Photoelectric Equation

$$hf = KE_{max} + \phi$$hf=KEmax​+ϕ

Where:

• $h$h = Planck’s constant
• $f$f = frequency
• $\phi$ϕ = work function

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4. Work Function (φ)

Minimum energy required to remove an electron.$$\phi = hf_0$$ϕ=hf0​

Important:

• Depends only on material

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5. Kinetic Energy of Electrons

$$KE_{max} = hf – \phi$$KEmax​=hf−ϕ

Insight:

• Depends only on frequency

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6. Stopping Potential

$$eV_0 = KE_{max}$$eV0​=KEmax​

Important:

• Independent of intensity

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7. Effect of Intensity

• Increases number of emitted electrons (current)
• Does NOT affect kinetic energy

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8. Photon Properties

• Energy: $E = hf$E=hf
• Momentum: $p = \frac{h}{\lambda}$p=λh​
• Zero rest mass
• Travels with speed $c$c

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9. De Broglie Hypothesis

All particles have wave nature:$$\lambda = \frac{h}{p}$$λ=ph​

Important:

• Significant for microscopic particles

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10. Davisson-Germer Experiment

• Proved wave nature of electrons
• Confirmed de Broglie hypothesis

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PART 2: ATOMS (BOHR MODEL)

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11. Bohr’s Postulates

• Electrons revolve in fixed circular orbits
• Energy is quantized
• No radiation in stable orbit

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12. Radius of Orbit

$$r_n \propto n^2$$rn​∝n2

• Higher orbit → larger radius

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13. Energy of Electron

$$E_n = -\frac{13.6}{n^2} \, \text{eV}$$En​=−n213.6​eV

Key Point:

• Negative energy → electron is bound

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14. Energy Transition

• Upward jump → absorption of energy
• Downward jump → emission of photon

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15. Frequency of Emitted Radiation

$$\nu = \frac{\Delta E}{h}$$ν=hΔE​

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16. Hydrogen Spectrum

• Produces line spectrum

Important Series:

• Lyman (UV)
• Balmer (visible)
• Paschen (IR)

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17. Ionization Energy

Energy required to remove electron from ground state.

• For hydrogen: 13.6 eV

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18. Energy Quantization

Energy exists in discrete levels, not continuous.

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19. Important IIT JEE Formulas

• $hf = KE + \phi$hf=KE+ϕ
• $\lambda = \frac{h}{p}$λ=ph​
• $E = hf$E=hf
• $p = \frac{h}{\lambda}$p=λh​
• $E_n = -\frac{13.6}{n^2}$En​=−n213.6​
• $\nu = \frac{\Delta E}{h}$ν=hΔE​

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20. Common Mistakes

❌ Thinking intensity affects kinetic energy
❌ Confusing work function and threshold frequency
❌ Mixing photon energy with electron energy
❌ Forgetting negative energy concept

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21. Quick Revision Tips

• Photoelectric effect → particle nature
• De Broglie → wave nature of matter
• Bohr model → quantized orbits
• Energy transitions → spectral lines

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Conclusion

Dual Nature + Atoms is a very easy and high-scoring unit in IIT JEE.

Focus on:

• Photoelectric equations
• De Broglie relation
• Bohr model formulas
• Energy transitions

👉 With proper revision, you can secure full marks from this chapter easily.