Shortcut Methods

Shortcuts & Tricks for Numerical Problems in Optics

Diffraction:

  • Single Slit:
    • For the central maximum:

width=2λL/d

  • For the first secondary maxima (on either side of central maxima): θ=sin1λd

where (\lambda) is the wavelength, (L) is the distance between the slit and the screen, and (d) is the slit width.

  • Multiple Slits:
  • Use dsinθ=mλ to determine the number of slits (N):

N=width of central maximawidth of individual slits

Interference:

  • Double-Slit:

  • Path difference for constructive interference: dsinθ=mλ

  • Fringe spacing: Δy=λL/d

where (\Delta y) is the distance between adjacent bright fringes, (L) is the distance to the screen, and (\theta) is the angle from the central maximum.

  • Thin Films:

-For constructive interference: 2nt=mλ,  m=0,1,2,3

Polarization:

  • Brewster’s Angle:

θB=tan1(n2n1)

where (\theta_B) is Brewster’s angle, and (n_1) and (n_2) are the refractive indices of the two media.

  • Intensity of Transmitted Light: It=I0cos2θ

where (I_t) is the intensity of transmitted light, (I_0) is the intensity of incident light, and (θ) is the angle between the polarization direction of the incident light and the transmission axis of the polarizer.

Note: These are just a few general shortcuts and tricks for numerical problems in optics. Depending on the specific question, you may need to use a combination of these methods and apply other relevant equations and concepts from optics.