NESA Physics Electromagnetic Spectrum
7 sample questions with marking guides and sample answers · Avg. score: 77.5%
Which of the following did Maxwell contribute to the understanding of the nature of light?
Explanation of atomic emission spectra
Prediction of the speed of electromagnetic waves
Experimental support for the particle model of light
Experimental confirmation of light beyond the visible spectrum
Reveal Answer
Explanation of atomic emission spectra
Incorrect. The explanation of atomic emission spectra was developed later by Niels Bohr and other quantum physicists using quantum mechanics, not by Maxwell.
Prediction of the speed of electromagnetic waves
Correct. Maxwell formulated a set of equations that predicted the existence of electromagnetic waves traveling at the speed of light (), establishing that light itself is an electromagnetic wave.
Experimental support for the particle model of light
Incorrect. Maxwell's work firmly established the wave model of light; experimental support for the particle model came later from Einstein's explanation of the photoelectric effect.
Experimental confirmation of light beyond the visible spectrum
Incorrect. Maxwell provided the theoretical framework for electromagnetic waves, but experimental confirmation of invisible light like infrared and radio waves was achieved by scientists like Herschel and Hertz.
Electromagnetic radiation is
extremely high-frequency radiation emitted from the nucleus of some radionuclides.
the emission of energy as waves or particles, especially high-energy particles, that causes ionisation.
a wave of energy produced by an oscillating electric charge, resulting in mutually perpendicular electric and magnetic fields.
radiant energy consisting of synchronised oscillations of electric and magnetic fields, or electromagnetic waves, propagated at the speed of light in a vacuum.
Reveal Answer
extremely high-frequency radiation emitted from the nucleus of some radionuclides.
This describes gamma rays specifically, which are just one type of high-energy electromagnetic radiation, rather than the general definition for all electromagnetic radiation.
the emission of energy as waves or particles, especially high-energy particles, that causes ionisation.
This defines ionizing radiation, which includes high-energy particles (like alpha and beta particles) in addition to waves, and excludes non-ionizing electromagnetic radiation like radio waves and visible light.
a wave of energy produced by an oscillating electric charge, resulting in mutually perpendicular electric and magnetic fields.
While this correctly describes the mechanism of generation and the geometry of an electromagnetic wave, Option D provides the more complete and formal definition of the radiant energy itself and its propagation characteristics.
radiant energy consisting of synchronised oscillations of electric and magnetic fields, or electromagnetic waves, propagated at the speed of light in a vacuum.
This is the comprehensive definition of electromagnetic radiation, characterizing it as radiant energy composed of synchronized oscillating electric and magnetic fields that propagate at the speed of light () in a vacuum.
A physics student hears a clap of thunder shortly after observing a flash of lightning.
Which one of the following statements best describes the sound associated with the clap of thunder and the visible light associated with the flash of lightning?
Both the sound and the visible light are examples of transverse waves.
Both the sound and the visible light are examples of longitudinal waves.
Sound is an example of a transverse wave and visible light is an example of a longitudinal wave.
Sound is an example of a longitudinal wave and visible light is an example of a transverse wave.
Reveal Answer
Both the sound and the visible light are examples of transverse waves.
Incorrect. While visible light is a transverse wave, sound is a longitudinal wave because it propagates through compressions and rarefactions in the air.
Both the sound and the visible light are examples of longitudinal waves.
Incorrect. While sound is a longitudinal wave, visible light is an electromagnetic wave, which is transverse because its fields oscillate perpendicular to the direction of travel.
Sound is an example of a transverse wave and visible light is an example of a longitudinal wave.
Incorrect. This option reverses the wave types. Sound requires particle oscillation parallel to propagation (longitudinal), while light consists of perpendicular oscillating fields (transverse).
Sound is an example of a longitudinal wave and visible light is an example of a transverse wave.
Correct. Sound is a longitudinal wave because air particles oscillate parallel to the wave's direction, whereas visible light is a transverse wave because its electromagnetic fields oscillate perpendicular to its direction of travel.
Which one of the following statements best describes the type of light produced from different types of light sources?
Light from a laser is coherent and has a very narrow range of wavelengths.
Light from an incandescent lamp is coherent and has a range of wavelengths.
Light from an incandescent lamp is incoherent and has a very narrow range of wavelengths.
Light from a single-colour light-emitting diode (LED) is coherent and contains a very wide range of wavelengths.
Reveal Answer
Light from a laser is coherent and has a very narrow range of wavelengths.
Lasers produce light through stimulated emission, resulting in light waves that are in phase (coherent) and highly monochromatic (a very narrow range of wavelengths).
Light from an incandescent lamp is coherent and has a range of wavelengths.
Incandescent lamps produce light through thermal emission, which is a random process that generates incoherent light, not coherent light.
Light from an incandescent lamp is incoherent and has a very narrow range of wavelengths.
While incandescent light is indeed incoherent, it emits a continuous spectrum over a very wide range of wavelengths, not a narrow one.
Light from a single-colour light-emitting diode (LED) is coherent and contains a very wide range of wavelengths.
Light from an LED is generated by spontaneous emission, making it incoherent, and a single-color LED emits a relatively narrow band of wavelengths, not a wide range.
Electromagnetic waves are produced by an oscillating electric charge resulting in an interaction between magnetic and electric fields.
How are these two fields aligned?
parallel to each other
varied in their wavelengths
synchronised in their oscillations
intersected at the peaks of their amplitudes
Reveal Answer
parallel to each other
The electric and magnetic fields in an electromagnetic wave are always perpendicular () to each other and to the direction of wave propagation.
varied in their wavelengths
Since the electric and magnetic fields are coupled components of the same wave, they always share the same wavelength and frequency.
synchronised in their oscillations
The electric and magnetic fields oscillate in phase, meaning they reach their maximum amplitudes and zero crossings at the exact same time and position.
intersected at the peaks of their amplitudes
This description is inaccurate; because the fields are in phase, they cross the axis of propagation at the same time (the nodes), not at the peaks of their amplitudes.
Describe how electromagnetic radiation is propagated by the interaction between electric and magnetic fields.
Reveal Answer
Oscillating charged particles induce a magnetic field. This subsequently induces an electric field perpendicular to the magnetic field.
| Descriptor | Marks |
|---|---|
Describes the production of an induced magnetic field | 1 |
Describes formation of an induced electric field, perpendicular to the magnetic field | 1 |
An electron would produce an electromagnetic wave when it is
stationary.
in a stable hydrogen atom.
moving at a constant velocity.
moving at a constant speed in a circular path.
Reveal Answer
stationary.
Incorrect. A stationary electron produces a static electric field but no magnetic field, meaning it cannot generate an electromagnetic wave.
in a stable hydrogen atom.
Incorrect. According to quantum mechanics, an electron in a stable atomic orbit does not emit radiation; if it did, it would continuously lose energy and spiral into the nucleus.
moving at a constant velocity.
Incorrect. An electron moving at a constant velocity has zero acceleration, and electromagnetic waves are only produced by accelerating charges.
moving at a constant speed in a circular path.
Correct. An electron moving in a circular path is constantly changing direction, meaning it experiences centripetal acceleration. According to classical electromagnetism, any accelerating charge emits electromagnetic waves.