Find Wavelength of Light Through Slits

[daisyi]

Almost done guys :)

If the first order bright lines formed by two slits at a distance of 2 meters are 3 cm apart, find the wavelength of the light if the slit separation is 9.12x10^-3 cm.

So, to find the wavelength, this is what I did.

wavelength = 9.12 * 10^-5m * (2m/(3*10^-2m)) = .00608m.

i'm not understanding what i am doing wrong. any input would be helpful. Thanks!

 

[Doc Al]

You need to understand the formula for the double slit diffraction pattern. The distance of the first maxima (from the central maxima) is given by:
y = \frac{\lambda L}{d}

 

[daisyi]

y = \frac{\lambda L}{d}

right, so y=9.12*10^-5m, d = 2m and L = 3*10^-2m.

 

[Doc Al]

right, so y=9.12*10^-5m, d = 2m and L = 3*10^-2m.

Nope:
L is the distance to the screen
d is the distance between the slits
y is the distance of the first maxima to the center (this is half of the distance between those maxima).

 

[daisyi]

thanks, i got it :)