double slit and wavelength urgent!!!

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alvan15
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Describe the change to the pattern seen on the screen when the violet laser is replaced by a green laser. Assume the brightness of the central maximum is the same for both lasers

obviously the fringe spacing increases, but why would the width of diffraction pattern increase as well
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J__
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(Original post by alvan15)
Describe the change to the pattern seen on the screen when the violet laser is replaced by a green laser. Assume the brightness of the central maximum is the same for both lasers

obviously the fringe spacing increases, but why would the width of diffraction pattern increase as well


The green light has a greater wavelength then the violet light, so greater diffraction occurs when passing through the slit. This causes the fringe spacing to increase so the fringes will have a greater width with the green light.

Hope this helps
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Eimmanuel
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(Original post by alvan15)
Describe the change to the pattern seen on the screen when the violet laser is replaced by a green laser. Assume the brightness of the central maximum is the same for both lasers

obviously the fringe spacing increases, but why would the width of diffraction pattern increase as well

For the diffraction pattern, we may want to look at this posting.
https://www.thestudentroom.co.uk/sho...0#post71582920

Or

Have a look at the ACTIVE FIGRUE 38.7 in the following link.

https://books.google.com.sg/books?id...epage&q&f=true

The intensity distribution is described by the following equation:

 I = I_{\text{max}} \cos^2 \left ( \dfrac {\pi a \sin \theta}{\lambda} \right ) \left [\dfrac {\sin( \frac{\pi w \sin \theta}{\lambda })}{\frac{\pi w \sin \theta } {\lambda} } \right ]^2

w is the width of the slit.
a is the separation between two slits

If you look at ACTIVE FIGURE 38.7, you would see a blue dotted line – this line is described by the square brackets term in the above equation which is "diffraction pattern" term.

If you want to see how the above intensity distribution changes when wavelength changes, go to the following link.
http://www.cengage.com/physics/book_...E7/AF_3807.swf

and changes the variable to see how fringes pattern changes.

Hope it helps.
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alvan15
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(Original post by Eimmanuel)
For the diffraction pattern, we may want to look at this posting.
https://www.thestudentroom.co.uk/sho...0#post71582920

Or

Have a look at the ACTIVE FIGRUE 38.7 in the following link.

https://books.google.com.sg/books?id...epage&q&f=true

The intensity distribution is described by the following equation:

 I = I_{\text{max}} \cos^2 \left ( \dfrac {\pi a \sin \theta}{\lambda} \right ) \left [\dfrac {\sin( \frac{\pi w \sin \theta}{\lambda })}{\frac{\pi w \sin \theta } {\lambda} } \right ]^2

w is the width of the slit.
a is the separation between two slits

If you look at ACTIVE FIGURE 38.7, you would see a blue dotted line – this line is described by the square brackets term in the above equation which is "diffraction pattern" term.

If you want to see how the above intensity distribution changes when wavelength changes, go to the following link.
http://www.cengage.com/physics/book_...E7/AF_3807.swf

and changes the variable to see how fringes pattern changes.

Hope it helps.
Thank you for such detail help, definitely helped
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