1. Tardigrade
  2. Question
  3. Physics
  4. A monochromatic plane wave of speed c and wavelength λ is diffracted at a small aperture. The diagram illustrates successive wavefronts (vibrating in the same phase). After what time will some portion of the wavefront XY reach P ? <img class=img-fluid question-image alt=Question src=https://cdn.tardigrade.in/q/nta/p-0z9xz6edh5cr.png />

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A monochromatic plane wave of speed c and wavelength $\lambda $ is diffracted at a small aperture. The diagram illustrates successive wavefronts (vibrating in the same phase). After what time will some portion of the wavefront $XY$ reach $P$ ?

Question

NTA AbhyasNTA Abhyas 2020Wave Optics

Solution:

This distance between the 2 successive lines (wavefronts) is $\lambda $ . This is for both the straight and curved lines.
So, wavefront XY is separated by a distance of $3 \lambda $ from the wavefront that has reached point P.
Distance that needs to be traveled $= 3 \lambda $
Speed of light $= c$
Speed = Distance/Time
Time = distance/speed $= \frac{3 \lambda }{c}$