27.3 Young’s Double Slit Experiment
3 min read•june 18, 2024
reveals light's wave nature through patterns. When light passes through two slits, it creates alternating bright and on a screen, demonstrating constructive and .
The experiment's results depend on , , and screen distance. It showcases , where waves combine to form a resultant wave, and provides evidence for light's .
Young's Double Slit Experiment
Young's double slit interference pattern
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Top images from around the web for Young's double slit interference pattern
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- consists of alternating bright and dark fringes on a screen
- are areas of where waves from the two slits arrive in , reinforcing each other (light waves)
- Dark fringes are areas of where waves from the two slits arrive out of phase, canceling each other (sound waves)
- is the brightest and widest as it is equidistant from both slits, resulting in maximum (laser light)
- Bright fringes become dimmer and narrower moving away from the center because the increases, reducing the degree of constructive interference (water waves)
- Spacing between fringes depends on the wavelength of light and the distance between the slits
- Larger wavelengths (red light) or smaller slit separations result in wider
- Smaller wavelengths (blue light) or larger slit separations lead to narrower fringe spacing
- The experiment demonstrates the principle of , where waves combine to produce a resultant wave
Angles of constructive vs destructive interference
- Constructive interference occurs when the path length difference is an integer multiple of the wavelength
- , where is the slit separation, is the angle, is an integer (0, ±1, ±2, ...), and is the wavelength
- Destructive interference occurs when the path length difference is a half-integer multiple of the wavelength
- , where is an integer (0, ±1, ±2, ...)
- To calculate the angles:
- Solve the equation for using the given slit separation () and wavelength ()
- For constructive interference, use integer values of (0, ±1, ±2, ...)
- For destructive interference, use half-integer values of (±0.5, ±1.5, ±2.5, ...)
Path length difference in interference
- Path length difference determines the phase relationship between waves arriving at a point on the screen
- When the path length difference is an integer multiple of the wavelength, waves arrive in phase, causing constructive interference and resulting in a bright fringe ( meeting crest)
- When the path length difference is a half-integer multiple of the wavelength, waves arrive out of phase, causing destructive interference and resulting in a dark fringe (crest meeting )
- As the angle from the central axis increases, the path length difference between the waves from the two slits also increases, leading to alternating regions of constructive and destructive interference ()
- The degree of constructive or destructive interference depends on the exact path length difference
- Maximum constructive interference occurs when the path length difference is exactly an integer multiple of the wavelength (complete reinforcement)
- Partial constructive or destructive interference occurs for path length differences between integer and half-integer multiples of the wavelength (partial reinforcement or cancellation)
Wave properties and experimental setup
- The experiment requires to produce a clear interference pattern
- occurs as light passes through the narrow slits, causing the waves to spread out
- The is the experimental apparatus used to observe the interference pattern
- Young's experiment provides evidence for the wave-particle duality of light, showing both wave-like interference and particle-like behavior
Key Terms to Review (37)
Acceleration due to gravity: Acceleration due to gravity is the rate at which an object accelerates when falling freely under the influence of Earth's gravitational pull. Its standard value on Earth's surface is approximately $9.81 \text{ m/s}^2$.
Angular Dependence: Angular dependence refers to the relationship between the angle of incidence or observation and the behavior or properties of a physical phenomenon. It is a fundamental concept that describes how the outcome or measurement of a system varies with the angle at which it is observed or interacted with.
Bright Fringes: Bright fringes are the regions of constructive interference that occur in the interference pattern created by a Young's double slit experiment. These bright regions correspond to the points where the waves from the two slits meet in phase, resulting in an increase in the intensity of the observed light.
Central Bright Fringe: The central bright fringe is the brightest interference pattern that appears at the center of the screen in both Young's double slit experiment and single slit diffraction. It represents the region where the waves from the two slits or the single slit constructively interfere, resulting in maximum intensity of the light.
Coherent: Coherent light consists of waves that have a constant phase difference, the same frequency, and the same waveform. It is essential for creating clear interference patterns.
Coherent Light: Coherent light refers to a type of light in which the waves are in phase with each other, meaning they have a constant phase difference. This allows for the waves to interfere constructively and destructively, leading to the observation of interference patterns in various optical phenomena, such as Young's double-slit experiment, thin-film interference, and microscopy enhanced by the wave characteristics of light.
Constructive interference: Constructive interference occurs when two or more waves superpose to form a resultant wave with a greater amplitude than any of the individual waves. This happens when the phase difference between the waves is an integer multiple of $2\pi$ radians.
Constructive Interference: Constructive interference is a phenomenon that occurs when two or more waves, such as sound or light waves, interact and reinforce each other, resulting in an increase in the amplitude or intensity of the combined wave. This principle is fundamental to understanding various wave-related phenomena in physics, including superposition, interference, and diffraction.
Constructive interference for a double slit: Constructive interference occurs when two or more waves superpose to form a wave with a larger amplitude. In a double slit experiment, this happens when the path difference between the two waves is an integer multiple of the wavelength.
Crest: In the context of wave physics, a crest is the highest point of a wave, where the displacement of the medium is maximum. It represents the peak or the highest amplitude of a wave as it propagates through a medium.
D sin θ = (m + 1/2) λ: This equation represents the condition for constructive interference in a Young's double-slit experiment, where d is the distance between the two slits, θ is the angle of the interference pattern, m is an integer representing the order of the interference, and λ is the wavelength of the light used.
D sin θ = m λ: The equation $$d \sin \theta = m \lambda$$ describes the condition for constructive interference in the context of wave phenomena, particularly in the Young's Double Slit Experiment. Here, 'd' represents the distance between the slits, 'θ' is the angle at which constructive interference occurs, 'm' is the order of the interference (an integer), and 'λ' is the wavelength of the light used. This relationship highlights how waves can interact and create patterns of light and dark, which is fundamental to understanding wave behavior.
Dark Fringes: Dark fringes are the regions of destructive interference that occur in the interference pattern produced by a Young's double-slit experiment. These dark regions represent the areas where the waves from the two slits cancel each other out, resulting in a lack of light intensity.
De Broglie wavelength: The de Broglie wavelength is the wavelength associated with a particle and is inversely proportional to its momentum. It highlights the wave-particle duality of matter.
Destructive interference: Destructive interference occurs when two waves meet in such a way that their crests and troughs cancel each other out, resulting in a reduced or zero amplitude. This phenomenon is a result of the superposition principle.
Destructive Interference: Destructive interference occurs when two waves of the same frequency and amplitude interfere in such a way that they cancel each other out, resulting in a decrease or complete elimination of the wave amplitude at certain points. This phenomenon is observed in various wave-based systems, including sound, light, and electromagnetic waves.
Destructive interference for a double slit: Destructive interference for a double slit occurs when waves from two slits arrive at a point out of phase, resulting in a reduction or cancellation of wave amplitude. This leads to dark fringes on an interference pattern.
Diffraction: Diffraction is the bending and spreading of waves as they encounter an obstacle or an aperture. This phenomenon occurs when waves, such as light or sound, encounter an edge or an opening, causing them to bend and spread out, rather than traveling in a straight line.
Double-Slit Interferometer: A double-slit interferometer is an optical device used to demonstrate the wave-like behavior of light. It consists of a light source that illuminates a screen with two narrow, parallel slits, creating an interference pattern on the screen as the light waves from the two slits interact with each other.
Fringe Spacing: Fringe spacing refers to the distance between adjacent bright or dark fringes in an interference pattern, such as the one observed in Young's double-slit experiment. It is a crucial parameter that determines the characteristics and behavior of the interference pattern.
Incoherent: Incoherent light consists of waves that have random phases and do not maintain a fixed phase relationship over time. It is characterized by its lack of consistent interference patterns.
Interference: Interference is the phenomenon that occurs when two or more waves interact with each other, resulting in the creation of a new wave pattern. This concept is central to understanding the behavior of light and other forms of electromagnetic radiation in the context of Young's Double Slit Experiment and the Rayleigh Criterion for the limits of resolution.
Interference Pattern: An interference pattern is the distribution of light intensity created by the interference of two or more waves. It is a result of the constructive and destructive interference of waves, leading to regions of high and low intensity.
M: The variable 'm' is a fundamental quantity that represents mass, a fundamental property of an object that quantifies the amount of matter it contains. This term is central to the understanding of Hooke's Law, oscillations, and the Young's Double Slit Experiment, as mass plays a crucial role in these physical phenomena.
Order: Order in wave optics refers to the integer value that characterizes the position of a bright or dark fringe in an interference pattern. Higher-order fringes correspond to higher integer values of this order.
Path Length Difference: The path length difference refers to the difference in the distance traveled by light waves originating from the same source and reaching a particular point after passing through different paths. This concept is crucial in understanding the interference patterns observed in the Young's Double Slit Experiment.
Phase: Phase refers to the position of a wave in its cycle, typically measured as the angle or fraction of a complete oscillation. It is a crucial concept in understanding the behavior of waves, such as their interference and diffraction patterns.
Slit Separation: Slit separation refers to the distance between two closely spaced slits in Young’s double slit experiment, which is fundamental in demonstrating the wave nature of light. This distance is crucial for determining the interference pattern formed on a screen, as it affects the spacing and intensity of the bright and dark fringes observed in the pattern. The slit separation influences how waves from each slit interact with one another, leading to constructive or destructive interference.
Superposition: Superposition is the principle that when two or more waves overlap, the resulting wave displacement is the sum of the individual wave displacements. This principle applies to all types of waves, including mechanical and electromagnetic.
Superposition: Superposition is the principle that when two or more waves or oscillations occur at the same time and location, their net displacement is the vector sum of the individual displacements. This concept is fundamental to the understanding of various wave phenomena, including interference and diffraction.
Thomas Young: Thomas Young was a renowned British polymath who made significant contributions to the fields of optics, wave theory, and surface tension. His work laid the foundations for our understanding of the wave nature of light and the principles of interference, diffraction, and thin-film interference.
Trough: A trough is a local minimum or low point in a wave pattern, occurring between two crests or peaks. It is a fundamental concept in the study of wave phenomena and is particularly relevant in the context of Young's Double Slit Experiment.
Wave-Particle Duality: Wave-particle duality is a fundamental concept in quantum physics that describes the dual nature of light and matter, where they exhibit characteristics of both waves and particles depending on the context and experimental conditions. This principle is central to understanding the behavior of electromagnetic radiation and the properties of subatomic particles.
Wavelength: Wavelength is a fundamental characteristic of waves, representing the distance between consecutive peaks or troughs in a wave. It is a crucial parameter that describes the spatial extent of a wave and is closely related to other wave properties such as frequency and speed.
Young's Double Slit Experiment: Young's Double Slit Experiment is a classic physics experiment that demonstrates the wave-like nature of light. It involves the interference of light passing through two narrow slits, resulting in a pattern of bright and dark regions on a screen.
θ (Theta): Theta (θ) is a fundamental mathematical symbol used to represent an angle in various contexts, including rotation, wave interference, and resolution limits. It is a Greek letter that serves as a variable or parameter to quantify and analyze angular relationships and phenomena.
λ: Lambda (λ) is a Greek letter that represents the wavelength of a wave, which is the distance between two consecutive peaks or troughs of the wave. This term is particularly important in the context of Young's Double Slit Experiment and the Rayleigh Criterion, as the wavelength of light is a crucial factor in understanding the behavior of light and the limits of optical resolution.