Question

Spectroscopy Springtime weather in temperate climates is often unsettled . A drizzly rainy day can suddenly become sunny . Often this leads to a rainbow , when water droplets in the atmosphere spread sunlight into colorful arcs across the sky . The same principles underlying a rainbow are the basis of a powerful observational technique called spectroscopy , which is applied in nearly all fields of science . In this lab you will investigate the dispersion of light and interpret observed spectra to determine the composition of a distant object.

Answer 1

Suppose we are determining the composition of star a distant object. First as we know if we use a spectrometer that is using a diffraction grating , when the light from a source is allowed to fall on diffraction grating and then it is observed from telescope we find the spectra of the light according to Braggs' law I. .e ,where d is the distance between two consecutive slit of grating , theta is angle and lambda is the wavelength of the light. Now for sodium lamp we get wavelength at 5890 angstrom or for good spectrometers this is a doublet line. This is the emission spectra. Now for absorption spectra the the line we are getting in emission spectrum at the same place we get a dark line which shows that this element is absorbing the radiation. Now doing same for star, taking its spectra we get lots of lines in colour and as well as in dark lines. As we know the energy spectrum for each element is unique. So from the spectrum we come to know that what elements are in the star from their emission and absorption spectra. From it we determine tha composition of star.