This PPT explains about the Comparison of prism and grating spectra

1. COMPARISON OF PRISM AND GRATING
SPECTRA

2. • Prism spectrum
• 1.A prism produces
only one spectrum
• 2.all the light energy
emerging from a
prism is concentrated
in a single spectrum.
So the intensities of
spectral lines are
large
• Grating spectrum
• 1.A grating gives a
number of spectra of
different orders on
each side of the central
maximum
• 2.in a grating most of
the is concentrated in
te centre maximum and
the rest is distributed in
the spectra of different
orders.so the
intensities of spectral
lines are very small

3. • 3.The prism spectrum
is prodused by
dispersion,Disperision
is due to different
velocities of light
through the prism for
different wavelengths
• 4.In a prism the
deviation is least for
red greatest for violet
colour
• 5.The prism spectrum
depends on the
material of the prism
• 3.The grating spectrum
is formed by diffraction
of light .For maximum
intensity the angle of
diffraction is different
for different
wavelengths
• 4.In a grating the
deviationis least for
violet and greatest for
red
• 5.The grating spectra
are independent on the
material of the grating

4. • 6.The dispersive power of
a prism is
• DS/dY α 1/Y^3
• Thus there is greater
dispersion in the violet
region (short wave
lengths) than in the red
region.The spectrum
obtained with a prism is
irrational spectrum
• 7.The resolving power of
a prism is small .Hence
usually the prism
spectrum does not show
spectrum does not show
the fine structure of
spectral lines
• 6.the dispersive power
of a grating is
• d0/dY=n/(a+b)cos0
• It is a constant foe a
particular order .Thus
the spectral lines are
evenly distributed.the
spectrum obtained is
said to be normal
• 7.the resolving power of
the grating is large
Hence the grating
spectrum shows te fine
structure of spectral
lines

5. THANK YOU