A physics teacher drew a ray diagram on the board as shown in Figure 8 below and asked the…
A physics teacher drew a ray diagram on the board as shown in Figure 8 below and asked the following questions to the students. State whether the answer of the student is correct or incorrect. Correct the incorrect response with an explanation in brief.
(i)
Teacher: The path difference between $S_1P$ and $S_2P$ at a point P on the screen of two interfering light waves is exactly $1\cdot2 \times 10^{-6}\text{ m}$. If the light emitted by the source has a wavelength of $600\text{ nm}$, can anyone tell me whether a bright or a dark fringe will form at the point P?
Student: Dark fringe will be obtained.
(ii)
Teacher: Two students performed the same Young’s double slit experiment. One student obtained wider fringes. What is the possible reason for this observation?
Student: The student who obtained wider fringes must have increased the distance between the two slits.
(iii)
Teacher: If one of the slits is closed with a finger while performing the experiment, what change will be noticed on the screen?
Student: The screen will get illuminated uniformly.
Answer
Answer (i)
AIWritten by AI (gemini) - it can contain mistakes.
Incorrect. A bright fringe will be obtained. The path difference is $\Delta x = 1\cdot2 \times 10^{-6}\text{ m}$ and $\lambda = 600\text{ nm} = 6 \times 10^{-7}\text{ m}$. Thus $\Delta x = 2\lambda$ (an integral multiple of $\lambda$, $n = 2$), which satisfies the condition for constructive interference.
Answer (ii)
AIWritten by AI (gemini) - it can contain mistakes.
Incorrect. The fringe width is $\beta = \frac{\lambda D}{d}$. To obtain wider fringes (larger $\beta$), the slit separation $d$ must be decreased, not increased.
Answer (iii)
AIWritten by AI (gemini) - it can contain mistakes.
Incorrect. Instead of uniform illumination, a single-slit diffraction pattern will be observed on the screen.
From ISC 2027 Specimen Physics Paper 1, question 13.