Dual Nature of Radiation & Matter — Previous-Year Questions

Q1. A metal of work function 2 eV is illuminated by light of wavelength 400 nm. Maximum KE of ejected photoelectrons:

Q2. Threshold wavelength for a metal with φ = 2.48 eV:

Q3. If light intensity is doubled (same frequency), what changes?

Q4. Slope of V_s vs f graph equals:

Q5. Photoelectric current saturates because:

Q6. If a metal's φ = 4 eV is illuminated by 300 nm light, K_max is:

Q1. Work function of a metal is 3.1 eV. Threshold wavelength:

Q2. Below threshold frequency, increasing the intensity:

Q3. If threshold frequency is 6 × 10¹⁴ Hz, work function is:

Q4. Which metal would NOT emit photoelectrons with green light (λ = 550 nm)?

Q5. Why is threshold frequency a function only of metal, not of light?

Q1. If frequency of incident light is doubled (from 2f₀ to 4f₀), K_max:

Q2. K_max vs f graph is a straight line with slope:

Q3. If K_max = 1 eV for light of frequency 6 × 10¹⁴ Hz, work function is:

Q4. Increasing intensity of incident light:

Q5. For two metals of work functions φ₁ < φ₂, on a K_max vs f graph:

Q1. If the intensity of light incident on a photocathode is doubled, the photoelectric current:

Q2. Doubling the intensity of light affects:

Q3. Saturation current is reached when:

Q4. A photocell receives light of intensity 10 W/m² and frequency 6×10¹⁴ Hz over area 1 cm². Photons arriving per second:

Q5. At a fixed frequency, plot of photocurrent vs intensity is:

Q1. Light of frequency 8 × 10¹⁴ Hz on a metal of φ = 2 eV gives stopping potential of:

Q2. If intensity of light is doubled, V_s:

Q3. Slope of V_s vs f graph is:

Q4. If wavelength of incident light is halved (still above threshold), V_s:

Q5. Stopping potential of a photocell does NOT depend on:

Q1. Davisson-Germer experiment (1927) established:

Q2. Which experiment best demonstrates the PARTICLE nature of light?

Q3. de Broglie wavelength of an electron of momentum 6.6 × 10⁻²⁴ kg·m/s is:

Q4. The wave nature of a cricket ball (m = 0.15 kg, v = 30 m/s) is undetectable because:

Q5. Complementarity principle (Bohr) states:

Q1. de Broglie wavelength of an electron accelerated through 100 V:

Q2. An electron has K = 200 eV. Its de Broglie wavelength:

Q3. If an electron and a proton have the same KE, the ratio λ_e/λ_p is:

Q4. A particle of mass 1 g moves at 1 m/s. Its de Broglie wavelength:

Q5. When the velocity of an electron is doubled, its de Broglie wavelength:

Q1. Davisson-Germer experiment used electrons accelerated through 54 V. Their de Broglie wavelength:

Q2. Electron diffraction off a crystal demonstrates:

Q3. If the accelerating voltage of electrons in an electron microscope is increased by 4×, the resolution improves by:

Q4. Electrons of KE 50 eV are diffracted by a crystal with d = 0.5 Å. First-order angle (Bragg):

Q5. G.P. Thomson's experiment showed:

Q1. The wave function |ψ|² represents:

Q2. Standing matter waves in a 1D box of length L of an electron give allowed wavelengths:

Q3. Group velocity of a matter wave equals:

Q4. Why don't we observe matter-wave interference for a baseball?

Q5. Schrödinger equation describes:

Q1. An electron's position is measured to within Δx = 0.1 nm. Minimum uncertainty in momentum:

Q2. Heisenberg's uncertainty principle is a consequence of:

Q3. The principle does NOT apply to:

Q4. An excited atomic state has lifetime 10⁻⁸ s. Its energy uncertainty is approximately:

Q5. Why are atoms stable per the uncertainty principle?