CBSE 2023 · Region 3 · Set 1 · Q35 · 4 marks

Diffraction of light is bending of light around the corners of an object whose size is comparable with the wavelength of light. Diffraction actually defines the limits of ray optics. This limit for optical instruments is set by the wavelength of light. An experimental arrangement is set up to observe the diffraction pattern due to a single slit. Answer the following questions based on the above :
(a)
How will the width of central maximum be affected if the wavelength of light is increased?
(b)
Under what condition is the first minimum obtained ?
Write two points of difference between interference and diffraction patterns.

Wave OpticsDiffractionUnderstandcase_studymedium

\begin{itemize} \item[(a)] \(\displaystyle \beta_{o} \propto \lambda\) \(\displaystyle \beta_{o}\) will increase with increase in wavelength. \item[(b)] When path difference \(\displaystyle a \theta=\lambda\) or at an angle ; \(\displaystyle \theta \approx \lambda / a\) \item[(c)] Differences \begin{tabular}[t]{\|l\|l\|} Interference Pattern	Diffraction Pattern
(i) All the maxima are equally spaced. (ii)The dark fringe is having zero intensity. (iii) All the maxima are of the same intensity.
(iv)
Alternatively:--It is obtained by the superposition of two waves originating from two sources/slits.	(i) Width of Central bright maxima is twice the width of the other maxima. (ii) The dark fringe is not completely dark. (iii) There is a sharp decrease in the intensity of maxima after the central bright maxima. (iv)
It is obtained by the superposition of waves from points on a single slit.

Marking-scheme solution