Question

A grating is 3.4 cm wide. A spectral line of wavelength 578 nm is observed at 39∘ in order 3.

The grating is made up of ---- lines. (How many?)

Answer #1

We use the equation for a grating

d = distance between the lines in a grating

= angle =
39^{o}

m = order = 3

= wavelength =
578 nm = 578 x 10^{-9} m

So, d = (3 x 578 x 10^{-9} )/sin(39) m = 2.76 x
10^{-6} m = 2.76 x10^{-4} cm

No. of lines per cm = 1/d = 1/2.76 x10^{-4}
cm^{-1} = 3623.19 cm^{-1}

Width of the grating = 3.4 cm

No of lines = 3623.19 x 3.4 lines = 12318.846 lines =
**12319 lines (rounding off)**

Hence, there are **12319 lines in the grating**

A diffraction grating is made up of slits of width 400 nm with
separation 1100 nm. The grating is illuminated by monochromatic
plane waves of wavelength λ = 720 nm at normal incidence.
(a) How many maxima are there in the full
diffraction pattern? (b) What is the angular width
of a spectral line observed in the first order if the grating has
960 slits?
Question 2 :
A diffraction grating is made up of slits of width a
with...

A diffraction grating is made up of slits of width 400 nm with
separation 1100 nm. The grating is illuminated by monochromatic
plane waves of wavelength λ = 720 nm at normal incidence.
(a) How many maxima are there in the full
diffraction pattern? (b) What is the angular width
of a spectral line observed in the first order if the grating has
960 slits?

A diffraction grating is made up of slits of width 440
nm with separation 1300 nm. The grating is illuminated by
monochromatic plane waves of wavelength λ = 810 nm at normal
incidence. (a) How many maxima are there in the
full diffraction pattern? (b) What is the angular
width of a spectral line observed in the first order if the grating
has 1300 slits?

Light of wavelength 600 nm shines on a diffraction grating that
has 400 lines per cm. The light emerging from the grating hits a
screen 50 cm wide so that the central maximum is exactly in the
middle of the screen. Assume that the screen is 3 m from the
grating.
How many maxima appear on the screen?
(a)
4
(b)
6
(c)
7
(d)
5
(e)
3

A spectral line from a star is observed to have a wavelength of
656.5 nm. The rest wavelength of this line is 656.8 nm. (a) What is
the speed of the star, and (b) is it approaching or receding from
the Earth? (c) If the star’s emitted wavelength is the same as the
rest value, what is happening?

A-The first-order line of 584 nm light falling on a diffraction
grating is observed at a 16.6° angle. Calculate the number of lines
per centimetre on the grating.
B- At what angle will the second-order line be observed?

The hydrogen spectrum has a red line at 656 nm and a violet line
at 434 nm. What angular separation between these two spectral lines
is obtained with a diffraction grating that has 4440 lines/cm?
(Assume that the light is incident normally on the grating.)
first order
separation
°
second order
separation
°
third order
separation
°
The hydrogen spectrum has a red line at 656 nm and a violet line
at 434 nm. What angular separation between these two...

White light is spread out into its spectral components by a
diffraction grating. If the grating has 2055 lines per centimeter,
at what angle does red light of wavelength 640 nm appear in
first-order spectrum? (Assume that the light is incident normally
on the grating.)
°

A 550 lines/mm diffraction grating is illuminated by light of
wavelength 520 nm.
How many bright fringes are seen on a 3.7-m-wide screen located
2.1 m behind the grating?

he hydrogen spectrum has a red line at 656 nm and a violet line
at 434 nm. What angular separation between these two spectral lines
is obtained with a diffraction grating that has 4554 lines/cm?
(Assume that the light is incident normally on the grating.)
first order separation
°
second order separation
°
third order separation

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