Engineering Physics

14.8 Fraunhofer diffraction at double slit

The double slits have been represented as A₁B₁ and A₂B₂ in Fig. 14.11. The slits are narrow and rectangular in shape. The plane of the slits are perpendicular to plane of the paper. Let the width of both the slits be equal and it is ‘e’ and they are separated by opaque length ‘b’. A monochromatic plane wave front of wave length ‘λ’ is incident normally on both the slits.

 

Figure 14.11 Fraunhofer diffraction at double slits

 

Theory: Every point on the wave front in the slits will act as a source of secondary wavelets. The secondary wavelets travelling in the direction of OP₀ are brought to focus at ...