Topic 6: The Universe Flashcards
What is a diffraction grating?
A piece of material with lines on it that produce a spectrum which diffuses light.
What is a continuous emission spectrum?
A complete spectrum of colours showing all wavelengths of light.
What is a line emission spectrum?
A series of bright lines on a dark background. Produced by hot gases.
What is a line absorption spectrum?
A series of dark lines on a continuous emission spectrum. Produced by a cool gas with a hot continuous source behind it - such as a star.
What scientific device did Joseph von Fraunhofer create?
The spectroscope (which contained a diffraction grating).
What are Fraunhofer lines?
The line absorption spectrum of the Sun that allows you to determine what elements are present.
Do stars produce all wavelengths of light or not?
They do produce all wavelengths of light.
What is the Doppler effect?
The change in wavelength (and frequency) caused by the relative movement of a source of waves.
What is cosmological red shift?
The wavelength at which the radiation is originally emitted is lengthened as it travels through (expanding) space.
What is recessional velocity?
The velocity away from an observer.
What is Hubble’s law?
The speed of recession is proportional to the distance of the galaxy away from Earth.
What is cosmic microwave background radiation?
Radiation that started life as gamma waves but was stretched into longer wavelength microwaves by the Universe expanding. (It’s like the echo of the Universe’s radiation)
