Solve Maximum Number of Fringes Observed from Laser Beam on Grating

In summary: The diffracted light provides a series of bright and dark spots. The first order spots are the brightest, and the second order spots are the darkest.
  • #1
noobie!
58
0
i would like to ask a que regarding physical optic,so let's nt beating abt the bush,
QUE:A laser beam is incident on a 1.50 x 10^4 grove per inch diffraction grating.The wavelength of the light produced by the laser is 6.30nm and the interference pattern is observed on a screen 2.00m from the grating.Determine maximum number of fringes that can be observed?
here goes the solution but I am nt really clear of the solution:
d sin teta = m X lamda
sin teta=m.lamda.N/l <1
m< l/2N ans is 2.69.
tis is my que,why d=l/N wat does it represents for l/N ?then why do sin teta=m.lamda.N/l <1?why?is it because of polarized light is lesser than 1 while unpolarized light bigger than 1?thanks for your help!:smile:
 
Physics news on Phys.org
  • #2
d is distance between two successive groves, and N is the number of groves per meter.
And sin theta is always <1
 
  • #3
rl.bhat said:
d is distance between two successive groves, and N is the number of groves per meter.
And sin theta is always <1

oh..ya,thanks a lot,1 more doubt please,what does it mean with 1st order?is that mean a pair of fringe which involves bright and dark fringe?so as the same que as above i asked,so the m value is 2.69..so there are 5 fringes detected,m i wright?2 bright fringes and 2 dark fringes and 1 center max?please tell me if I am wrong?!thanks...
 
  • #4
When you observe the diffracted along the normal to the grating you see a bright spot. When you move on either side, at a certain angle, again you see bright spots. These are called the first order spots, because the satisfy the relation d*sin(theta) = lambda. If you move still further, again you can see bright spots, which satisfy the condition d*sin(theta) = 2*lambda. These are called second order spots. And so on.
 
  • #5
rl.bhat said:
When you observe the diffracted along the normal to the grating you see a bright spot. When you move on either side, at a certain angle, again you see bright spots. These are called the first order spots, because the satisfy the relation d*sin(theta) = lambda. If you move still further, again you can see bright spots, which satisfy the condition d*sin(theta) = 2*lambda. These are called second order spots. And so on.

then what about dark spot?is it after at certain angle u observed u saw bright spot at the same time it has dark spot?i;m so sorry for troubling you..:blushing:
 

1. What is the purpose of using a grating in a laser beam experiment?

The grating acts as a diffraction element, splitting the laser beam into multiple beams and creating a pattern of fringes. This allows for precise measurements and analysis of the laser's wavelength and other properties.

2. How does the number of fringes observed vary with the number of slits on the grating?

As the number of slits on the grating increases, the number of fringes observed also increases. This is because more slits allow for more diffraction and interference of the laser beam, resulting in a more complex pattern of fringes.

3. What factors affect the maximum number of fringes observed on a grating?

The maximum number of fringes observed on a grating is affected by the wavelength of the laser, the spacing of the slits on the grating, and the distance between the grating and the screen where the fringes are observed. Additionally, the angle of incidence of the laser beam and the quality of the grating can also impact the maximum number of fringes.

4. Can the maximum number of fringes be calculated or predicted?

Yes, the maximum number of fringes can be calculated using the grating equation, which takes into account the wavelength of the laser, the spacing of the slits, and the angle of incidence. However, other factors such as the quality of the grating and environmental conditions may affect the actual number of fringes observed.

5. How is the maximum number of fringes observed on a grating used in practical applications?

The maximum number of fringes observed on a grating can be used to accurately determine the wavelength of a laser, which is important in many fields such as optics, spectroscopy, and telecommunications. It can also be used to calibrate and test the quality of gratings used in various experiments and devices.

Back
Top