CBSE 2022 · Region 4 · Set 2 · Q7 · 3 marks
(a)The interference pattern is not observed in Young's double slit experiment when the two sources $\displaystyle \mathrm{S}_{1}$ and $\displaystyle \mathrm{S}_{2}$ are far apart. Explain.(b)Mention the conditions for the two sources to be coherent.(c)What is the effect on the interference pattern in a Young's double slit experiment, if the source of wavelength $\displaystyle \lambda$ is replaced by another source of wavelength $\displaystyle 1 \cdot 5 \lambda$, with the interference pattern still observable ?
(a)
The interference pattern is not observed in Young's double slit experiment when the two sources $\displaystyle \mathrm{S}_{1}$ and $\displaystyle \mathrm{S}_{2}$ are far apart. Explain.
(b)
Mention the conditions for the two sources to be coherent.
(c)
What is the effect on the interference pattern in a Young's double slit experiment, if the source of wavelength $\displaystyle \lambda$ is replaced by another source of wavelength $\displaystyle 1 \cdot 5 \lambda$, with the interference pattern still observable ?
Marking-scheme solution
a) Explanation $\displaystyle 1$
b) Condition for coherent source $\displaystyle 1$
c) Explanation $\displaystyle 1$
a) $\displaystyle \beta=\frac{\lambda D}{d}$, When space between point source increases, fringe width decrease. Interference pattern gets less and less sharp/ Interference pattern will not be observable.
Alternatively
On increasing separation between the slits the condition $\displaystyle \frac{s}{s}<\frac{\lambda}{d}$, will not be satisfied and interference pattern disappears.
b) Two sources must have same frequency and constant or zero phase difference / constant or zero path difference.
c) $\displaystyle \beta \propto \lambda$ fringe width will increase & intensity ( Brightness) of fringe will decrease.
Wave OpticsInterference of Light Waves and Young’s ExperimentUnderstandshort_answermedium
More from Wave Optics
- Assertion: In interference and diffraction of light, light energy reduces in one region producing a dark…2024 · asked 3×
- Assertion: In a Young's double-slit experiment, interference pattern is not observed when two coherent…2024 · asked 3×
- What are coherent sources? Why they are necessary for observing stable interference pattern? Draw a graph…2026 · asked 3×
- In a Young's double-slit experiment, the fringe width is found to be β. If the entire apparatus is immersed…2023 · asked 3×
- Assertion: In Young's double slit experiment all fringes are of equal width. Reason (R): The fringe width…2023 · asked 3×
- (i) A plane light wave propagating from a rarer into a denser medium, is incident at an angle i on the…2024 · asked 3×
- Assertion: Light added to light can produce darkness. Reason (R): When two coherent light waves interfere,…2026 · asked 3×
- In a Young's double-slit experiment, the screen is moved away from the plane of the slits. What will be its…2023 · asked 3×
CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.