Playbook
Dual Nature of Radiation and Matter
82 q - 2.04/paper - 32% HARD. The hardest chapter in the bank, and one of the narrowest: two equations carry all of it.
- Questions in the bank
- 82
- q/paper (2024–25 papers)
- 2.04
- Tagged HARD
- 32%
- Subtopics
- 2
Strand: Long Tail
When you’ll see it
Light falling on a metal — work function, threshold, stopping potential, photocurrent graphs — or the wavelength of a moving particle.
How this chapter is tested
82 q at 2.04 a paper, 32% HARD — the hardest chapter in the Physics bank. But it is also one of the narrowest: two equations carry all of it. Photoelectric Effect is 56 questions at 36% HARD; de Broglie Wavelength and Matter Waves is 26 at 23%.
The photoelectric equation is hν = φ + ½mv²_max, and eV₀ = ½mv²_max. Below the threshold frequency nothing is emitted whatever the intensity; above it, intensity sets the NUMBER of electrons (the current) and frequency sets their energy (the stopping potential). The graph questions test exactly that split.
de Broglie: λ = h/p = h/√(2mK) = h/√(2mqV). For an electron accelerated through V volts, λ ≈ 1.227/√V nm. Doubling the kinetic energy divides λ by √2.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Einstein's equation
hν = φ + K_max, K_max = eV₀. Threshold: hν₀ = φ. In eV: E = 1240/λ(nm).
Intensity vs frequency
Intensity raises the current and leaves V₀ unchanged; frequency raises V₀ and leaves the saturation current unchanged.
de Broglie wavelength
λ = h/√(2mK). Electron through V volts: λ = 1.227/√V nm.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Letting intensity change the stopping potential
Brighter light of the same frequency gives more electrons, not faster ones. The stopping potential does not move; the saturation current does.
Doubling the frequency doubles the energy
K_max = hν − φ. Doubling ν more than doubles K_max, because φ stays fixed. Ratio questions print the 'doubles' option.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Dual Nature of Radiation and Matter notesDrill every dual nature of radiation and matter question
82 questions from the bank, scoped to 2 bundled subtopics.
Drill one subtopic at a time
The 2 subtopics this playbook covers, in catalog order.
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