1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Light Questions - Please Help

  1. Feb 2, 2005 #1
    Light Questions - Please Help!!!

    I thought I was doing this problem right, but according to webassign I'm not, and I can't figure out what I've done wrong... please help!!

    1. A helium-neon laser emits light that has a wavelength of 632.8 nm. The circular aperture through which the beam emerges has a diameter of 0.500 cm. Estimate the diameter of the beam 16.0 km from the laser.

    >> Here's what I did:
    min angle = d/L = .005/16000 = 3.125e-7
    min angle = 1.22(lamda/D)
    -> min angle/1.22 = lambda/D
    3.125e-7/1.22 = 6.328e-7/D
    -> 6.328e-7/2.56e-7 = D = 2.47

    Not sure why this is wrong... :cry:

    2. The second-order bright fringe in a single-slit diffraction pattern is 1.50 mm from the center of the central maximum. The screen is 80.0 cm from a slit of width 0.600 mm. Assuming that the incident light is monochromatic, calculate the light's approximate wavelength.

    >> I'm not really sure how to start this at all. I know I'm looking for lambda and that a=6.0e-4m, L=0.800m, m=2

    Any ideas??
     
  2. jcsd
  3. Feb 2, 2005 #2
    For the second question, use this formula:

    [tex]\lambda = (\frac{x}{L}) (\frac{d}{n-\frac{1}{2}})[/tex]
     
  4. Feb 2, 2005 #3
    I plugged in that formula and got a wavelength of 750 nm... which webassign is still saying is wrong...

    Ack Im so confused!! :eek:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Light Questions - Please Help
  1. Help light question (Replies: 3)

  2. Light Question (Replies: 1)

  3. Light Question (Replies: 4)

Loading...