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NEET-XII-Physics

17: Light Waves

with Solutions - page 4
Qstn# iv-13-a Prvs-QstnNext-Qstn
  • #13-a
    Find the change in the optical path due to introduction of the plate. (b) What should be the minimum thickness t which will make the intensity at the centre of the fringe pattern zero? Wavelength of the light used is
    λ. Neglect any absorption of light in the plate.
    Ans : When the plate is placed in front of the slit, then the optical path difference is given by `` \left(\,\mathrm{\,\mu \,}-1\right)t``. (b) For zero intensity at the centre of the fringe pattern, there should be distractive interference at the centre.
    So, the optical path difference should be = `` \frac{\lambda }{2}``
    `` \,\mathrm{\,i\,}.\,\mathrm{\,e\,}.\left(\mu -1\right)t=\frac{\lambda }{2}``
    `` \Rightarrow t=\frac{\lambda }{2\left(\mu -1\right)}``
    Page No 381:
  • #13-b
    What should be the minimum thickness t which will make the intensity at the centre of the fringe pattern zero? Wavelength of the light used is
    λ. Neglect any absorption of light in the plate.
    Ans : For zero intensity at the centre of the fringe pattern, there should be distractive interference at the centre.
    So, the optical path difference should be = `` \frac{\lambda }{2}``
    `` \,\mathrm{\,i\,}.\,\mathrm{\,e\,}.\left(\mu -1\right)t=\frac{\lambda }{2}``
    `` \Rightarrow t=\frac{\lambda }{2\left(\mu -1\right)}``
    Page No 381: