This quiz covers the examinable content of Module 7: the electromagnetic spectrum, the wave nature of light, special relativity, and the quantum model of light. 19 multiple choice questions drawn from the 14 syllabus-aligned lessons.
25 questions — instant feedback
Q1. Which region of the electromagnetic spectrum has the highest photon energy?
Correct: C. Gamma rays have the highest frequency and therefore the highest photon energy ($E = hf$).
Q2. A diffraction grating with 500 lines/mm is used with light of wavelength 600 nm. The angle of the first-order maximum is:
Correct: B. $d = 1/(500\\times10^3) = 2.0\\times10^{-6}$ m. $\\sin\\theta = m\\lambda/d = 1 \\times 600\\times10^{-9}/(2.0\\times10^{-6}) = 0.30$. $\\theta = \\sin^{-1}(0.30) = 17.5°$.
Q3. In Young's double-slit experiment, decreasing the slit separation while keeping wavelength constant will:
Correct: A. Fringe spacing $\\Delta y = \\lambda L/d$ is inversely proportional to slit separation $d$. Decreasing $d$ increases $\\Delta y$.
Q5. Einstein's second postulate of special relativity states that:
Correct: B. The second postulate states that $c$ is invariant — all observers measure the same speed of light regardless of their motion.
Q6. A spaceship of proper length 300 m flies past Earth at $0.8c$. Earth observers measure its length as:
Correct: A. $\\gamma = 1/\\sqrt{1-0.64} = 1.667$. $L = L_0/\\gamma = 300/1.667 = 180$ m.
Q7. A particle has total energy $E = 3mc^2$. Its Lorentz factor is:
Correct: C. $E = \\gamma mc^2$, so $\\gamma = E/(mc^2) = 3$.
Q8. In the twin paradox, the travelling twin returns younger because:
Correct: D. The situation is asymmetric — the travelling twin must accelerate to turn around, changing inertial frames. The stay-at-home twin remains in a single inertial frame.
Q9. The photoelectric effect provides evidence that light:
Correct: B. The photoelectric effect cannot be explained by the wave model. It requires photons with discrete energy $E = hf$.
Q10. A metal has work function 2.0 eV. Light of frequency $8.0\\times10^{14}$ Hz shines on it. ($h = 4.14\\times10^{-15}$ eV·s). The maximum kinetic energy of emitted electrons is:
Correct: C. $hf = (4.14\\times10^{-15})(8.0\\times10^{14}) = 3.31$ eV. $E_{k,max} = 3.31 - 2.0 = 1.31$ eV.
Q14. According to wave-particle duality:
Correct: D. Wave-particle duality means quantum entities exhibit wave properties in some experiments and particle properties in others.
Q15. Which phenomenon is best explained by the wave model of light?
Correct: B. Young's double-slit interference is a wave phenomenon arising from superposition. The photoelectric effect and black-body radiation require quantum/particle explanations.
Q16. A proton ($m_p c^2 = 938$ MeV) has kinetic energy 938 MeV. Its speed is approximately:
Correct: A. $E_k = (\\gamma - 1)mc^2 = mc^2$, so $\\gamma = 2$. $v = c\\sqrt{1 - 1/4} = c\\sqrt{3}/2 = 0.866c$.
Q17. Light of wavelength 500 nm in air enters glass ($n = 1.5$). Its wavelength in glass is:
Correct: C. $\\lambda_{glass} = \\lambda_{air}/n = 500/1.5 = 333$ nm. Frequency stays constant; wavelength and speed decrease.
Q19. An X-ray photon has momentum $6.6\\times10^{-24}$ kg·m/s. Its wavelength is:
Correct: A. $\\lambda = h/p = 6.63\\times10^{-34}/(6.6\\times10^{-24}) = 1.0\\times10^{-10}$ m = 0.10 nm.
Q20. Which of the following is a consequence of special relativity?
Correct: D. The relativity of simultaneity is a core consequence of special relativity. Events simultaneous in one frame may not be in another.
Q21. A muon created at 15 km altitude travels at $0.995c$ toward Earth. In the muon's frame, it reaches the surface because:
Correct: C. In the muon's rest frame, Earth and its atmosphere approach at $0.995c$. The 15 km is length-contracted to $15/\\gamma \\approx 0.68$ km, which the muon easily traverses in its short lifetime.
Q23. Polarisation of light is best explained by:
Correct: A. Polarisation is the alignment of electric field oscillations in a transverse wave. It is inherently a wave phenomenon.
Q24. The principle of complementarity states that:
Correct: D. Bohr's complementarity principle: wave and particle aspects cannot be observed simultaneously in one experiment, but both are needed for a complete description.
Q25. Which of the following technologies relies on the particle nature of light?
Correct: C. Solar panels rely on the photoelectric effect — photons transferring energy to electrons to create current. This is a particle interaction. The others primarily use wave properties (diffraction, refraction, transmission).