SCSA Physics Science as a Human Endeavour
1 sample question with marking guides and sample answers
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.