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The phase difference between two wave trains giving rise to a dark fringe in Young's double slit interference experiment in ( \(n\) integer) (a) \(2 \pi n+\pi^{\prime} 4\) (b) \(2 \pi n+\pi\) (c) \(2 \pi n+\pi / 2\) (d) zero

Short Answer

Expert verified
The correct answer is (b) \(2 \pi n + \pi\).

Step by step solution

01

Understand the concept of dark fringes

In Young's double slit experiment, dark fringes occur when the path difference between the two waves is an odd multiple of half the wavelength. This results in the waves being out of phase by an odd multiple of \(\pi\), causing destructive interference.
02

Express the condition mathematically

The condition for destructive interference is when the phase difference \(\Delta \phi\) between the two waves is \((2n+1)\pi\), where \(n\) is an integer. This can be rewritten as \(2\pi n + \pi\).
03

Match the condition with the given options

Reviewing the options given:- (a) \(2 \pi n + \pi^{\prime} 4\)- (b) \(2 \pi n + \pi\)- (c) \(2 \pi n + \pi / 2\)- (d) zeroOption (b), \(2 \pi n + \pi\), matches the condition for a dark fringe in Young's double slit experiment.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Dark Fringe
In Young's Double Slit Experiment, when waves pass through two narrow slits, they overlap and interfere with one another, creating patterns of bright and dark bands on a screen. These patterns result from differences in the distance each wave travels from the slits to a given point on the screen.
Dark fringes are observed when the waves arrive out of phase, canceling each other out due to destructive interference. This occurs when the path difference between the two waves equates to half-integer wavelengths, like \( rac{1}{2} \lambda \), \( \frac{3}{2} \lambda \), etc.
Hence, a dark fringe appears when the path difference is an odd multiple of half the wavelength. This is where the waves meet in a way such that one wave's crest aligns with the other's trough. It's this perfect misalignment that creates the dark, unlit fringes. By understanding this, you can predict the positions of darkness in these interference patterns.
Destructive Interference
When two waves meet, they can interfere with each other constructively or destructively. Destructive interference occurs when two waves are out of phase by an odd multiple of \( \pi \).
This means the crest of one wave aligns with the trough of another, effectively canceling each other's effects. The result is a reduction in the overall wave amplitude at that point.
  • For light waves in Young's experiment, this phenomenon results in a dark fringe.
  • The mathematical expression for destructive interference when dealing with dark fringes is represented by the phase difference \( \Delta \phi = (2n+1)\pi \).
Where \( n \) is an integer that represents the number of the dark fringe. Valorizing the equation into realistic scenarios allows engineers and scientists to control light and wave patterns deliberately.
Phase Difference
The phase difference between two waves at a point is the measure of how far out of sync the waves are. It reveals whether the waves are in phase or out of phase.
In the context of Young's experiment, when waves are out of phase by an odd multiple of \( \pi \), they produce a dark fringe. The phase difference is critical in this setup because it determines the nature and position of the interference pattern.
  • The general formula for phase difference in this experiment is \( \Delta \phi = 2\pi n + \pi \), where \( n \) is an integer and represents the order of the dark fringe.
This formula is crucial for figuring out where the fringe patterns will appear on the screen. By manipulating the phase difference, variations in interference patterns can be introduced or controlled.
Path Difference
The concept of path difference describes the difference in distance each wave travels from the two slits to a point on the screen. In the case of a dark fringe, this path difference must equate to an odd multiple of half the wavelength.
This specific condition ensures that the waves are in complete destructive interference at that point. To calculate the path difference, consider how far each wave travels and their wavelength. The formula for this scenario is:
\[ \text{Path difference} = (2m+1) \frac{\lambda}{2} \]
Where \( m \) is an integer, representing the order of the dark fringe, and \( \lambda \) is the wavelength.
  • In Young's experiment, by knowing the wavelength and the path the waves take, it becomes straightforward to predict positions of dark and light fringes.
This understanding not only helps demonstrate fundamental physics principles but also has practical applications in fields like optics and engineering.

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Most popular questions from this chapter

The main difference in the phenomenon of interference and diffraction is that (a) diffraction is due to interaction of light from the same wavefront whereas interference is the interaction of waves from two isolated sources (b) diffraction is due to interaction of light from same wavefront, whereas the interference is the interaction of two waves derived from the same source (c) diffraction is due to interaction of waves derived from the same source, whereas the interference is the bending of light from the same wavefront (d) diffraction is caused by the reflected waves from a source whereas interference is caused due to refraction of waves from a source

The fact that light is transverse wave phenomenon derives its evidential support from the observation that (a) light is a wave motion (b) light is characterised by interference (c) light shows polarising effects (d) light can be diffracted

What is the minimum thickness of a soap bubble needed for constructive interference in reflected light if the light incident on the film is \(900 \mathrm{~nm}\) ? Assume the refractive index for the film is \(\mu=1.5\) (a) \(100 \mathrm{~nm}\) (b) \(150 \mathrm{~nm}\) (c) \(200 \mathrm{~nm}\) (d) \(250 \mathrm{~nm}\)

The necessary condition for an interference by two sources of light is that (a) two light sources must have the same wavelength (b) two point sources should have the same amplitude and same wavelength (c) two sources should have the same wavelength, nearly the same amplitude and have a constant phase angle difference (d) the two point sources should have a randomly varying phase differences

The wavefront is a surface in which (a) all points are in the same phase (b) there are pairs of points in opposite phase (c) there are pairs of points with phase difference \((\pi 2)\) (d) there is no relation between the phases

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