QCEVault

Quantum theory — Question 240

Original QCE Vault practice · 5 marks

Q240 · Practice questionComplex unfamiliar5 marks

QUESTION 240 (5 marks)

Two metals have work functions WA=2.00×10−19 JW_A=2.00\times10^{-19}\,\mathrm J and WB=3.00×10−19 JW_B=3.00\times10^{-19}\,\mathrm J. A monochromatic beam must produce a maximum photoelectron kinetic energy of at least 1.00×10−19 J1.00\times10^{-19}\,\mathrm J from each metal. Use h=6.626×10−34 J sh=6.626\times10^{-34}\,\mathrm{J\,s} and c=3.00×108 m s−1c=3.00\times10^8\,\mathrm{m\,s^{-1}}.
a)
Determine the longest wavelength that meets both requirements.
[3 marks]
b)
At a wavelength that meets the requirement, the beam intensity is reduced while its wavelength stays fixed. Explain the effects on maximum photoelectron kinetic energy and emission rate, assuming identical illumination area and unchanged surface conditions.
[2 marks]
Question linkSyllabus coverage

Related questions

  1. Q38 · Original practice · 1 mark
    Two idealised blackbody curves are shown. Curve T1T_1 has a shorter peak wavelength than curve T2T_2. Which statement is correct?
    Quantum theory
  2. Q39 · Original practice · 1 mark
    What is the energy of a photon of wavelength 500 nm500\,\text{nm}?
    Quantum theory
  3. Q40 · Original practice · 1 mark
    Photons of energy 6.0 eV6.0\,\text{eV} strike a metal with work function 2.2 eV2.2\,\text{eV}. The maximum photoelectron kinetic energy is
    Quantum theory
  4. Q41 · Original practice · 1 mark
    A metal has work function 2.50 eV2.50\,\text{eV}. Its threshold frequency is closest to
    Quantum theory