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For a demonstration, a professor uses a razor blade to cut a thin slit in a piece of aluminum foil. When she shines a laser pointer (λ=680nm) through the slit onto a screen 5.6 m away, a diffraction pattern appears. The bright band in the center of the pattern is 8.1 cm wide.
1. What is the width of the slit? answer in mm.

Respuesta :

Answer:

Slit width is 0.109 mm

Solution:

As per the question:

Wavelength of the light, [tex]\lambda = 680\ nm = 680\times 10^{- 9}\ m[/tex]

Distance from the screen, D = 5.6 m

Bright band in the center, 2x = 8.1 cm

x = 4.05 cm

Now,

To calculate the slit width, w:

From the diffraction:

[tex]sin\theta = \frac{\lambda}{w}[/tex]

For small angle:

[tex]sin\theta[/tex] ≈ [tex]tan\theta = \frac{x}{D}[/tex]

Also

[tex]\frac{x}{D} = \frac{\lambda }{w}[/tex]

Thus

[tex]w = \frac{D}{x}\times \lambda[/tex]

Substituting appropriate values in the above eqn:

[tex]w = \frac{6.5}{4.05\times 10^{-2}}\times 680\times 10^{- 9}[/tex]

w = 0.109 mm

1. The width of the slit is 0.109 mm.

Calculation of the slit width:

Since λ=680nm i.e. [tex]= 680 \times 10^{-9}m[/tex]

distance ,D = 5.6m

Bright band in the center, 2x = 8.1 cm

So,

x = 4.05 cm

Here we used diffraction:

[tex]sin \theta = \lambda \div \omega\\\\sin \theta = tan \theta = x \div D\\\\x \div D = \lambda \div \omega\\\\\omega = D \div x \times \lambda\\\\= 6.5 \div 4.05 \times 10^{-2} \times 680 \times 10^{-9}[/tex]

= 0.109 mm

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