How is spectrum formed

What is radio astronomy? What is a pulsar? Simple examples in the visible wavebands are shown below. One means by which a continuous spectrum can be produced is by thermal emission from a black body. This is particularly relevant in astronomy and is discussed in the next section. Astronomical spectra can be combination of absorption and emission lines on a continuous background spectrum.

Specific examples are discussed on another page. What gives rise to a continuous spectrum? Imagine heating a solid steel sphere with a blowtorch. When you remove the torch you can feel the heat being re-radiated by the sphere.

Applying the torch again puts more energy into the sphere - it gets hotter. Eventually it starts to glow dimly. As you continue heating it the sphere glows first red, then orange, yellow then white hot. If you were able to keep heating it sufficiently it may even glow blue hot. This sphere approximates what physicists call a black body. A black body radiator is a theoretical object that is totally absorbent to all thermal energy that falls on it, thus it does not reflect any light so appears black.

As it absorbs energy it heats up and re-radiates the energy as electromagnetic radiation. In the real world some objects approximate the behaviour of blackbodies. It is seen from the graph that the light having a higher wavelength, has a lower refractive index, so it bends less. For this reason, the refraction of red light is on the other hand, the wavelength of violet light is less, hence its refractive index more.

As a result, the refraction of violet light is more, i. When white light is dispersed into seven colours by a glass prism, different colours bend through different angles with respect to the incident ray. Of the seven colours, red light bends the least, while violet light bends the most. So, the rays of each colour emerge along different paths and appear distinct.

Hence, we get a spectrum of seven different colours. Report Error Is there an error in this question or solution? It covers all energies of light, extending from low-energy radio waves, to microwaves, to infrared, to optical light, to ultraviolet, to very high-energy X-rays and gamma rays.

Three types of spectra: continuous, emission line and absorption. Each element in the periodic table can appear in gaseous form and will produce a series of bright lines unique to that element. Hydrogen will not look like helium which will not look like carbon which will not look like iron Thus, astronomers can identify what kinds of stuff are in stars from the lines they find in the star's spectrum. This type of study is called spectroscopy.

The science of spectroscopy is quite sophisticated. From spectral lines astronomers can determine not only the element, but the temperature and density of that element in the star. The spectral line also can tell us about any magnetic field of the star. The width of the line can tell us how fast the material is moving.

We can learn about winds in stars from this.