Dual Nature of Radiation and MatterNEET MCQs with solutions
Dual Nature covers the photoelectric effect, Einstein's photoelectric equation, de Broglie hypothesis, Davisson-Germer experiment and photon properties. NEET tests photoelectric equation numericals (threshold frequency, stopping potential, max KE), de Broglie wavelength and photon energy/momentum calculations.
- Class
- 12 Physics
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- 24 questions
- In the RankUp app
- 567 questions
- ELITE questions
- 200
- NCERT topics
- 13
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Mixed Revision Test
The de Broglie wavelength associated with an electron accelerated through a potential difference of 81 V is:
Not quite — the answer is D.
Using λ = 12.27/√V Å: √81 = 9, so λ = 1.363 Å = 0.1363 nm ≈ 0.136 nm. Option B (1.36 nm) is 10× too large — from mistaking 1 Å = 1 nm instead of 1 Å = 0.1 nm.
Q2Introduction to Dual Nature of Radiation
If the wavelength of a photon is reduced to one-fourth of its original value, its energy becomes:
Not quite — the answer is D.
E = hc/λ means energy is inversely proportional to wavelength. Reducing λ to λ/4 multiplies E by 4. The trap is assuming direct proportionality.
Q3Numerical and Formula Based Concepts
Light of photon energy 4.2 eV falls on a metal having work function 2.2 eV. The stopping potential is:
Not quite — the answer is C.
Kmax=hν−φ=4.2−2.2=2.0 eV. Since Kmax=eVs, the stopping potential Vs=2.0 V. Option D (1.1 V) is wrong — it halves the answer, a sign that the student subtracted φ twice.
Q4Grand Test
An electron and a proton have equal de Broglie wavelengths. Which quantity must be equal for both particles?
Not quite — the answer is C.
From λ = h/p, equal wavelengths directly imply equal momenta. Speed differs because v = p/m and masses differ greatly. KE differs because K = p²/2m and masses differ. Only momentum is necessarily equal.
Q5Einstein's Photoelectric Equation
Einstein's work on the photoelectric effect provided direct support for which fundamental relation for the energy of a light quantum?
Not quite — the answer is A.
Einstein explained photoelectric emission using light quanta each carrying energy E=hν, directly supporting Planck's quantum relation. Options C and D are unrelated — C is Bohr's energy level formula and D is classical kinetic energy.
Q6Photoelectric Effect
Which fundamental result of the photoelectric experiment is correctly described?
Not quite — the answer is B.
At fixed frequency above threshold, more intensity means more photons per second, so more electrons are emitted and photocurrent increases. Stopping potential depends only on frequency, not intensity.
Q7Wave Nature of Matter (de Broglie Hypothesis)
Which of the following particles, all moving with the same velocity, has the largest de Broglie wavelength?
Not quite — the answer is A.
λ = h/(mv); at fixed v, λ is inversely proportional to mass. Electron has the smallest mass among the four, so it has the largest wavelength. Alpha particle has the largest mass and therefore the smallest wavelength.
Q8NCERT Miscellaneous Facts and PYQ Concepts
The work functions of Cs, K and Na are 2.14 eV, 2.30 eV and 2.75 eV respectively. Incident radiation has photon energy 2.20 eV. Which metal(s) can emit photoelectrons?
Not quite — the answer is A.
Photoemission requires hν ≥ φ. For Cs: 2.20 > 2.14 — emission occurs. For K: 2.20 < 2.30 — no emission. For Na: 2.20 < 2.75 — no emission. Option D is the trap — students confuse K (potassium) with Cs and select the wrong pair.
Q9Electron Emission
Which of the following is NOT a property of cathode rays?
Not quite — the answer is B.
Cathode rays are streams of electrons — negatively charged particles deflected by both electric and magnetic fields. They do produce fluorescence, heating effects, and cast sharp shadows. The only incorrect property listed is that they are not deflected by fields. Hence B.
Q10Hertz and Lenard's Observations
Heinrich Hertz observed the photoelectric phenomenon while performing experiments related to:
Not quite — the answer is B.
Hertz noticed UV illumination enhanced sparks during his EM-wave experiment, leading to photoelectric discovery. It was not related to radioactivity or atomic spectra experiments.
Q11Particle Nature of Light (Photon)
If c is the speed of light in vacuum, which set of statements about a photon is correct? Statement I: E = hν. Statement II: p = hν/c. Statement III: A photon has positive charge. Statement IV: A photon travels with speed c in vacuum.
Not quite — the answer is A.
E=hν and p=hν/c are correct. Photon is electrically neutral — statement III is false. Speed of photon in vacuum is always c. Hence I, II and IV are correct.
Q12Applications of Photoelectric Effect
A photoelectric cell is illuminated by a point source of light at distance d. If the distance is reduced to d/2, the number of photoelectrons emitted per second becomes:
Not quite — the answer is D.
Intensity from a point source varies as 1/d². Halving the distance quadruples the intensity. At fixed frequency above threshold, emission rate is proportional to intensity, so rate becomes 4n.
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Get RankUp on Google PlayQ13Davisson-Germer Experiment
In the Davisson-Germer experiment, the velocity of electrons emerging from the electron gun can be increased by:
Not quite — the answer is A.
K=eV, so a higher accelerating potential gives electrons more kinetic energy and thus greater velocity. Filament current controls emission rate, not individual electron energy.
Q14Introduction to Dual Nature of Radiation
Which of the following CORRECTLY identifies a phenomenon that demonstrates the particle nature of light?
Not quite — the answer is B.
The photoelectric effect demonstrates particle nature because photons transfer discrete quanta of energy to electrons. Interference, diffraction, and polarisation all demonstrate wave nature of light.
Q15Introduction to Dual Nature of Radiation
A photon has wavelength 600 nm. If its wavelength is changed to 300 nm, which pair correctly describes the change in frequency and energy?
Not quite — the answer is C.
c = νλ means halving λ doubles ν. Since E = hν, energy also doubles. Option B is the trap — students who correctly double frequency but misapply E ∝ λ get this wrong.
Q16Introduction to Dual Nature of Radiation
Which of the following phenomena supports the WAVE nature of radiation?
Not quite — the answer is A.
X-ray diffraction by crystal lattice is a classic wave phenomenon requiring interference of scattered waves. Compton scattering, photoelectric emission, and photon momentum transfer all demonstrate particle nature.
Q17Introduction to Dual Nature of Radiation
Which of the following statements about a photon is INCORRECT?
Not quite — the answer is D.
Photons are electrically neutral — they carry no charge. They possess energy hν, momentum h/λ, and travel at c. The incorrect statement is that a photon has a positive electric charge.
Q18Introduction to Dual Nature of Radiation
Consider the following statements about photon properties: I. Photon energy is hν. II. Photon momentum is h/λ. III. Photon rest mass is zero. IV. Photon carries positive electric charge. How many of the above statements are correct?
Not quite — the answer is B.
Statements I, II, and III are correct standard photon properties. Statement IV is false — photons are electrically neutral. Hence exactly 3 statements are correct.
Q19Introduction to Dual Nature of Radiation
A gamma-ray photon and a visible-light photon are compared. Which of the following is CORRECT?
Not quite — the answer is C.
Gamma rays have much shorter wavelengths and therefore higher frequencies than visible light. Since E = hν, gamma photons carry far greater energy. Option D is the trap — students who confuse wavelength and frequency invert the frequency comparison.
Q20Introduction to Dual Nature of Radiation
An electron and a photon have equal energies E. Which statement correctly compares their momenta?
Not quite — the answer is B.
For a photon p = E/c; for a non-relativistic electron p = √(2mE). These are generally unequal. Option A is the trap — equal energy does not imply equal momentum for matter vs. radiation.
Q21Introduction to Dual Nature of Radiation
Consider the following statements: I. E = hν for a photon. II. p = h/λ for a photon. III. E = pc for a photon in vacuum. IV. Photon rest mass is non-zero. How many of the above statements are correct?
Not quite — the answer is A.
Statements I, II, and III are all correct and mutually consistent: E = hν = hc/λ = pc. Statement IV is false — photon rest mass is zero. Hence exactly 3 statements are correct.
Q22Introduction to Dual Nature of Radiation
The momentum of a photon of energy 1 MeV in kg m/s is closest to:
Not quite — the answer is A.
p = E/c = 1.6×10⁻¹³ J / 3×10⁸ m/s ≈ 5.3×10⁻²² kg m/s. Option B is the trap — students who forget to divide by c leave the answer as raw energy in joules.
Q23Introduction to Dual Nature of Radiation
Source S1 emits 10¹⁵ photons/s of wavelength 5000 Å and S2 emits 1.02×10¹⁵ photons/s of wavelength 5100 Å. The ratio of power of S2 to S1 is:
Not quite — the answer is D.
P = Nhc/λ. P2/P1 = (N2/λ2)/(N1/λ1) = (1.02×10¹⁵/5100)/(10¹⁵/5000) = (1.02×5000)/5100 = 1.00. The trap is multiplying N×λ instead of dividing — giving 1.02 as a plausible wrong answer.
Q24Introduction to Dual Nature of Radiation
Two photons have wavelengths 300 nm and 600 nm respectively. If the momentum of the 600 nm photon is p, the momentum of the 300 nm photon is:
Not quite — the answer is C.
p = h/λ is inversely proportional to wavelength. The 300 nm photon has half the wavelength, so its momentum is 2p. Options B and D are traps for students who apply direct proportionality instead of inverse.
ELITE question · AIR under 50 level
This chapter has 200 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appKey Dual Nature Concepts
Quick revision: most questions in this chapter test these facts.
| Concept | Key Formula |
|---|---|
| Photoelectric equation | KE_max = hν − φ; φ = hν₀ (work function) |
| Stopping potential | eV₀ = KE_max = hν − φ; V₀ independent of intensity |
| Threshold frequency | ν₀ = φ/h; below ν₀, no emission regardless of intensity |
| de Broglie wavelength | λ = h/p = h/mv; λ = h/√(2mKE) |
| Photon energy | E = hν = hc/λ; momentum p = E/c = h/λ |
| Davisson-Germer | Confirmed wave nature of electrons; electron diffraction |
What the app covers in this chapter
567 questions in total, each with a detailed explanation.
| Mixed Revision Test | 117 |
| Introduction to Dual Nature of Radiation | 80 |
| Numerical and Formula Based Concepts | 60 |
| Grand Test | 55 |
| Einstein's Photoelectric Equation | 40 |
| Photoelectric Effect | 39 |
| Wave Nature of Matter (de Broglie Hypothesis) | 39 |
| NCERT Miscellaneous Facts and PYQ Concepts | 38 |
| Electron Emission | 20 |
| Hertz and Lenard's Observations | 20 |
| Particle Nature of Light (Photon) | 20 |
| Applications of Photoelectric Effect | 20 |
| Davisson-Germer Experiment | 19 |
Questions students ask
Is Dual Nature important for NEET?
Yes — photoelectric effect and de Broglie wavelength are tested every year. Einstein's equation and stopping potential calculations are NEET favourites.
Which topics should I revise first?
Master Einstein's photoelectric equation, stopping potential concept, threshold frequency, de Broglie wavelength formula for different particles, and photon energy-momentum relations.
How many questions from this chapter are on RankUp?
The RankUp app has 567 questions on Dual Nature of Radiation and Matter, including 200 ELITE questions. Every question has a detailed explanation.
