Question

When a beam of white light is passed through Sodium vapours and then through a Spectrometer. Spectrum so obtained has two dark lines Present in the yellow region. This spectrum is called
A) Band spectrum
B) Continuous spectrum
C) Absorption spectrum of sodium
D) Emission spectrum of sodium

Answer 1

Hint
The white bean when passed through sodium vapours uses the element and forms dark fringes when passed through the spectrometer. Sodium vapours also uses sodium in an excited state to produce light at wavelength near 589nm.

Complete Step By Step Solution
Let’s begin with what is white light striking. It’s given in the statement that. The white light passes through a Sodium vapor. As we know the working principle of Sodium Vapours lamp. Where low pressure is lightly efficient electrical spark of light. but yellow light restricts application to outdoor lighting. Such as street 1 am he which are widely used. The light beam there absorbs the sodium and efficiently provides the light.
Similarly, here the white light observed the sodium from its vapours and then through the spectrometer spectrum obtained 2 dark lines in the yellow region as we know the wavelength obtained in the lamp was ranging wavelength near to 589 nm.
Hence, the absorption takes place of sodium here, resulting in an absorption spectrum of sodium.
Option C is the correct answer.

Note
If the white line passes through vapours of different element and the color of light it emits depends on the range of wavelength it ranging like for Red-(700,635) nm, orange – (635,590) nm, yellow - (590,560) nm, green – (560,520) nm, cyan – (520,490) nm, blue - (490, 450) nm, violet – (450,400) nm.