Module 7: Electromagnetic Spectrum Flashcards
What is James Clerk Maxwell’s contribution to the unification of electricity and magnetism?
Maxwell unified electricity and magnetism into a single theory, demonstrating that electric fields and magnetic fields are interrelated as an electromagnetic wave.
How did Maxwell predict the existence of electromagnetic waves?
Maxwell predicted electromagnetic waves by showing that oscillating electric and magnetic fields can propagate through space as waves.
What did Maxwell predict about the velocity of electromagnetic waves?
Maxwell calculated the velocity of electromagnetic waves and found it to be approximately equal to the speed of light. This led him to propose that light itself is an electromagnetic wave.
Describe the propagation of electromagnetic waves.
Electromagnetic waves propagate through space as oscillating electric and magnetic fields perpendicular to each other.
Name a historical method used to determine the speed of light.
One historical method was conducted by Ole Rømer in 1676, who observed the timing of Jupiter’s moons and concluded that light has a finite speed.
How is the speed of light related to the measurement of time and distance today?
The speed of light is a fundamental constant used to define the meter in terms of the distance light travels in a vacuum in a specific time interval.
How can discharge tubes be used to examine spectra?
Discharge tubes, containing gases that emit light when electrically excited, produce characteristic spectral lines that can be analysed to identify elements and study their properties.
How does spectroscopy help identify elements?
Spectroscopy identifies elements by analysing the unique spectral lines emitted or absorbed by an element, which correspond to specific electron transitions within its atoms.
What information can be obtained from spectra produced by reflected sunlight or incandescent filaments?
Spectra from reflected sunlight or incandescent filaments show a continuous range of wavelengths, indicating the presence of multiple elements and providing information about temperature and composition.
How can the spectra of stars provide information about surface temperature?
The spectra of stars reveal their surface temperature through the distribution of wavelengths emitted. Hotter stars emit more blue and ultraviolet light, while cooler stars emit more red and infrared light.
How do the spectra of stars indicate their rotational and translational velocity?
The Doppler shift in the spectral lines of stars indicates their rotational and translational velocity. A redshift means the star is moving away, while a blueshift means it is approaching. Broadening of spectral lines can indicate rotation.
How can stellar spectra provide information on the density of a star?
The density of a star can be inferred from the width and intensity of its spectral lines. Higher density environments cause broader and more pressure-broadened spectral lines.
What information about chemical composition can be obtained from stellar spectra?
Stellar spectra reveal the chemical composition of a star by displaying the characteristic absorption or emission lines of various elements present in the star’s atmosphere.
