Figure shows standard two slits arrangement \( S_1 \), \( S_2 \). \( P_1 \) and \( P_2 \) are two maxima points on either side of P. At point \( P_2 \) on the screen there is a hole behind \( P_2 \) two slits arrangement with slits \( S_3 \) and \( S_4 \) and pattern obtained on second screen, which of the following is correct:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Regular two slits pattern on the second screen
\( P_2 \) is a maximum of the first pattern, so light comes out through the hole at \( P_2 \). The small hole then acts as a point source for the second arrangement, just as S does for \( S_1 \) and \( S_2 \).
Light from this one source reaches \( S_3 \) and \( S_4 \), so the two slits are coherent sources. Their waves interfere and form the regular two-slit pattern of bright and dark fringes on the second screen.
Option (2) Regular two slits pattern on the second screen — Correct. The hole at a bright point acts as a source, and \( S_3 \), \( S_4 \) act as coherent sources.
NCERT (2026-27):
Interference of Light Waves and Young’s Experiment – “… Light waves spread out from S and fall on both S1 and S2. S1 and S2 then behave like two coherent sources because light waves coming out from S1 and S2 are derived from the same original source … The spherical waves emanating from S1 and S2 will produce interference fringes on the screen GG′, as shown in Fig. 10.12(b).”