EmSAT Achieve (UAE) · Physics

Waves, Electromagnetism and Modern Physics

26 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 26 questions

  1. A sound wave of frequency 680 Hz travels through air at 340 m/s. What is its wavelength?
  2. A light ray in glass (refractive index n = 1.50) strikes a glass-air boundary. What is the critical angle for total internal reflection? (n_air = 1.00)
  3. Two point charges of +4.0 µC and -6.0 µC are separated by a distance of 0.30 m in a vacuum. What is the magnitude of the electrostatic force between them? (k = 9.0 × 10⁹ N·m²/C²)
  4. In a simple DC circuit, two resistors of 6.0 Ω and 12.0 Ω are connected in parallel across an ideal 24 V battery. What is the total current drawn from the battery?
  5. A proton enters a uniform magnetic field of 0.50 T with a velocity of 4.0 × 10⁶ m/s perpendicular to the field lines. What magnetic force acts on the proton? (q_p = 1.6 × 10⁻¹⁹ C)
  6. A flat coil of 50 turns with an area of 0.040 m² is placed perpendicular to a magnetic field that decreases uniformly from 0.80 T to 0.20 T in 0.30 seconds. What is the magnitude of the induced EMF?
  7. Monochromatic light shines on a metal surface whose work function is 2.30 eV. If the incident photons have an energy of 3.80 eV, what is the maximum kinetic energy of the emitted photoelectrons?
  8. A radioactive isotope has a half-life of 6.0 hours. If a pure sample initially contains 80 mg of this isotope, how much remains after 24 hours?
  9. An object is placed 20 cm in front of a thin converging lens with a focal length of 15 cm. What is the image distance and the nature of the image?
  10. What happens to the capacitance of an isolated parallel-plate capacitor if a dielectric slab with dielectric constant κ = 4 is inserted between the plates?
  11. A fire truck emitting an 800 Hz siren approaches a stationary observer at 30 m/s. If the speed of sound in air is 330 m/s, what frequency is heard by the observer?
  12. In a Young's double-slit experiment, monochromatic light of wavelength 600 nm passes through slits separated by 0.20 mm. The fringe pattern is observed on a screen 1.5 m away. What is the distance bet…
  13. A straight wire of length 0.80 m carrying a current of 5.0 A is placed at an angle of 30° to a uniform magnetic field of 0.40 T. What magnetic force acts on the wire?
  14. An electron is accelerated from rest through a potential difference of 100 V. What is its resulting kinetic energy in joules? (e = 1.6 × 10⁻¹⁹ C)
  15. Which electromagnetic wave region possesses photons with the greatest frequency and highest quantum energy?
  16. A step-down transformer has 1200 primary turns and 60 secondary turns. If an alternating voltage of 240 V is supplied to the primary winding, what is the output secondary voltage?
  17. A 10 µF capacitor is connected across a 50 V battery until fully charged. How much electrical energy is stored within its electric field?
  18. What is the de Broglie wavelength of an electron traveling at 2.0 × 10⁶ m/s? (h = 6.63 × 10⁻³⁴ J·s, m_e = 9.11 × 10⁻³¹ kg)
  19. Three resistors of 4.0 Ω, 6.0 Ω, and 12.0 Ω are connected in parallel. What is their combined equivalent resistance?
  20. According to special relativity, what happens to the measured length of a spacecraft moving past an observer at 0.8c along its direction of motion?
  21. A magnetic flux through a stationary loop of wire changes from 0.15 Wb to 0.45 Wb over an interval of 0.05 seconds. What magnitude of EMF is induced in the loop?
  22. In a nuclear fission reaction, a total mass defect of 0.020 u occurs. Taking 1 u = 931.5 MeV, how much energy is liberated by this fission event?
  23. Which phenomenon provides conclusive evidence for the wave nature of light rather than a purely classical particle nature?
  24. An electric heater rated at 1500 W operates connected to a 120 V power supply. What is the electrical resistance of the heating element?
  25. What is the electric field strength at a distance of 0.20 m from an isolated point charge of +2.0 µC in a vacuum? (k = 9.0 × 10⁹ N·m²/C²)
  26. A metal rod of length 0.50 m moves at 4.0 m/s perpendicular to a uniform magnetic field of 0.60 T. What motional EMF is induced across its ends?

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