A physics instructor wants to project a spectrum of visible-light colors from 400 nm to 700 nm as part of a classroom demonstration. She shines a beam of white light through a diffraction grating that has 700 lines per mm, projecting a pattern on a screen 2.9 m behind the grating. How wide is the spectrum corresponding to m=1?

Respuesta :

Answer:

Explanation:

Given

[tex]Slit\ width=d=\frac{10^{-3}}{700}=1.428\times 10^{-6} m[/tex]

Distance of screen from light source [tex]D=2.9 m[/tex]

[tex]\lambda _1=400 nm[/tex]

[tex]\lambda _2=700 nm[/tex]

we know in slit Experiment

[tex]d\sin \theta=n\lambda [/tex], where [tex]\theta [/tex]=angle between the path and a line from the slits to the screen

[tex]1.428\times 10^{-6}\cdot \sin \theta =1\times 400\times 10^{-9}[/tex]

[tex]\sin \theta =0.28011[/tex]

[tex]\theta =16.26^{\circ}[/tex]

and [tex]\tan \theta =\frac{y}{D}[/tex]

where y is the position of First maxima corresponding [tex]\lambda _1[/tex]

[tex]y_1=D\tan \theta [/tex]

[tex]y_1=0.845 m[/tex]

calculations for  [tex]\lambda _2[/tex]

[tex]d\sin \theta=n\lambda _2[/tex]

[tex]1.428\times 10^{-6}\cdot \sin \theta =1\times 700\times 10^{-9}[/tex]

[tex]\sin \theta '=0.4901[/tex]

[tex]\theta '=29.34^{\circ}[/tex]

[tex]\tan \theta '=\frac{y'}{D}[/tex]

for n=1

[tex]y_1'=D\tan \theta '[/tex]

[tex]y_1'=2.9\times 0.5622=1.63 m[/tex]

Spectrum Width [tex]=y_1'-y_1[/tex]

[tex]=0.785 m[/tex]

                   

0.785m is the width of the spectrum which corresponds to m=1.

What is width?

This is defined as the measurement of a body from side to side and usually has the shortest dimension.

Slit width = d = 10⁻³ / 700 = 1.428 ˣ 10⁻⁶m

In slit experiment dsinθ = nλ

1.428 ˣ 10⁻⁶m ˣ sinθ = 1 ˣ 400 ˣ 10⁻⁹

sinθ = 0.28011

θ = 16.26°

tanθ = y/D

y1 = Dtanθ

y1 = 0.845m

dsinθ2 = nλ2

1.428 ˣ 10⁻⁶m ˣ sinθ = 1 ˣ 700 ˣ 10⁻⁹

sinθ2 = 0.4901

θ2 = 29.34°

tanθ2 = y2/D

y2 = Dtanθ2

 = 2.9 × 0.5622 = 1.63m

Spectrum Width = y2 - y

                             = 1.63m - 0.845m

                                = 0.785m.

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