Explanation

(d) Fraunhofer lines are certain dark lines observed in the otherwise continuous spectrum of the sum. According to Fraunhofer, these dark lines represent the absorption spectrum of the vapours surrounding the sun. The sun consists of a hot central core called photosphere, which is at an extremely high temperature = $1.4\ \times 10^{7}$ K. it is surrounded by less dense, luminous and highly compressed gases. They are said to form sun’s atmosphere. A continuous spectrum
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containing radiations of all wavelengths is emitted by the sun’s atmosphere . surrounding this , is another sphere of vapours and gases at a comparatively lower temperature (6000 K). At the time of total solar eclipse, photosphere is covered. Emission lines from vapours of elements in chromosphere appear as bright lines. So, all Fraunhofer lines are changed into bright coloured lines.