Experiment Number: 02
ANALYSIS OF STELLAR SPECTRUM
Aim: To analyze the stellar spectrum given and to determine
the temperature of the star.
Principle: A star can be safely treated as a black body. Its
spectrum also resemble to a greater extent to the same. If we
can make use of the Planck’s black body radiation formula and
find out the temperature of the black body (in case of star) and
we have to find flux at their corresponding wavelength.
Formula: This explains feature of the black body, radio
spectrum of the star
Fᴀ ∝
Where
𝟏
𝝀𝒔
[𝒆
𝟏
𝒉𝒄/𝝀𝒌𝑻 −𝟏
]
wm⁻²
𝜆 is the wavelength (m)
h is the Planck’s constant
k is the Boltzmann’s constant
T is the temperature (K)
Nature of the Graph
Tabular column:
Sl no
1
2
3
4
5
6
Sl no
1
2
3
4
5
6
7
8
9
10
11
STANDARD WAVELENGTH (m) SCALE READING IN × 10⁻²m
STANDARD WAVELENGTH
SCALE READING
ℎ𝑐 1
(
𝛾 𝜆₂
T=
2.303 log
−
1
)
𝜆₁
𝐹𝜆₂
( )
𝐹𝜆₁
+5 log
𝜆₂
( )
𝜆₁
PROCEDURE:
*The given spectra are pasted on board in convenient manner
to observe from the travelling microscope.
*The readings are taken in a travelling microscope for standard
wavelength 4000, 5000 and 6000A⁰.
*The Calibration curve drawn taking travelling microscope
reading verses standard wavelength.
*The microscope reading verses radiation flux.
RESULT:
The temperature of the star is found to be ___________ A⁰.