Diffraction - Young Double-slit Experiment

  • What is diffraction?
  • Understanding the Young double-slit experiment
  • Experimental setup
  • Interference pattern
  • Conditions for constructive interference
  • Conditions for destructive interference

What is Diffraction?

  • The bending of waves around obstacles or through openings
  • It occurs for all types of waves, including light and sound waves
  • Diffraction causes wave interference, leading to patterns of light and dark regions

Understanding the Young Double-slit Experiment

  • Conducted by Thomas Young in 1801
  • Demonstrates the wave-like nature of light
  • Consists of two narrow slits illuminated by a coherent light source
  • Displays an interference pattern on a screen placed behind the slits

Experimental Setup

  • Coherent light source (laser)
  • Double-slit apparatus with adjustable slit separation (d)
  • Screen placed behind the slits
  • Distance between screen and slits (D)

Interference Pattern

  • On the screen, a pattern of light and dark regions is observed
  • Bright regions correspond to constructive interference
  • Dark regions correspond to destructive interference
  • Result of the superposition of light waves from each slit

Conditions for Constructive Interference

  1. Both waves must have the same wavelength (λ)
  1. Both waves must be in phase (peak aligns with peak, trough aligns with trough)
  1. Path difference between the two waves must be an integer multiple of the wavelength Example: Constructive interference occurs at point P on the screen if the path difference (Δx) between the two waves is an integer multiple of the wavelength (λ).

Conditions for Destructive Interference

  1. Both waves must have the same wavelength (λ)
  1. Waves must be out of phase (peak aligns with trough)
  1. Path difference between the two waves must be a half-integer multiple of the wavelength Example: Destructive interference occurs at point Q on the screen if the path difference (Δx) between the two waves is a half-integer multiple of the wavelength (λ).

Equation for Path Difference

  • Path difference (Δx) = d * sinθ
  • For constructive interference, Δx = m * λ (where m is an integer)
  • For destructive interference, Δx = (m + 0.5) * λ (where m is an integer)
  • θ is the angle between the central maximum and the point on the screen
  • d is the slit separation

Example: Calculation of Path Difference

  • Slit separation (d) = 0.1 mm
  • Wavelength of light (λ) = 600 nm
  • Angle (θ) = 30 degrees
  • Path difference (Δx) = d * sinθ
  • Path difference = (0.1 * 10^(-3)) * sin(30 degrees)
  • Calculate the value of the path difference

Recap

  • Diffraction is the bending of waves around obstacles or through openings
  • The Young double-slit experiment demonstrates the wave-like nature of light
  • Constructive interference occurs when the path difference is an integer multiple of the wavelength
  • Destructive interference occurs when the path difference is a half-integer multiple of the wavelength

Diffraction - Young Double-slit Experiment

  • What is diffraction?

  • Understanding the Young double-slit experiment

  • Experimental setup

  • Interference pattern

  • Conditions for constructive interference

  • Conditions for destructive interference

  • Equation for path difference

  • Example calculation of path difference

  • Recap

  • Summary and key takeaways

Conditions for Destructive Interference

  • Waves must have the same wavelength (λ)
  • Waves must be out of phase (peak aligns with trough)
  • Path difference between the two waves must be a half-integer multiple of the wavelength
  • Destructive interference provides dark regions on the screen
  • The dark regions occur when the waves cancel each other out

Equation for Path Difference

  • Path difference (Δx) = d * sinθ
  • For constructive interference, Δx = m * λ (where m is an integer)
  • For destructive interference, Δx = (m + 0.5) * λ (where m is an integer)
  • θ is the angle between the central maximum and the point on the screen
  • d is the slit separation Example: At an angle of 45 degrees, the path difference between two waves with a slit separation of 0.1 mm and a wavelength of 600 nm can be calculated using the equation.

Example Calculation of Path Difference

  • Slit separation (d) = 0.1 mm
  • Wavelength of light (λ) = 600 nm
  • Angle (θ) = 45 degrees
  • Path difference (Δx) = d * sinθ
  • Path difference = (0.1 * 10^(-3)) * sin(45 degrees)
  • Calculate the value of the path difference Example: For the given values, the path difference can be calculated as follows:

Recap

  • Diffraction is the bending of waves around obstacles or through openings
  • The Young double-slit experiment demonstrates the wave-like nature of light
  • Constructive interference occurs when the path difference is an integer multiple of the wavelength
  • Destructive interference occurs when the path difference is a half-integer multiple of the wavelength
  • The interference pattern results from the superposition of waves from the two slits
  • The pattern consists of bright and dark regions on the screen

Summary and Key Takeaways

  • Diffraction is the bending of waves around obstacles or through openings.
  • The Young double-slit experiment demonstrates the wave-like nature of light.
  • Constructive interference occurs when the path difference is an integer multiple of the wavelength, resulting in bright regions on the screen.
  • Destructive interference occurs when the path difference is a half-integer multiple of the wavelength, resulting in dark regions on the screen.
  • The interference pattern is a result of the superposition of waves from the two slits.
  • The pattern can be observed on a screen placed behind the slits.
  • Understanding interference in the Young double-slit experiment is crucial for comprehending the wave-particle duality of light.

Diffraction - Young Double-slit Experiment

  • What is diffraction?

  • Understanding the Young double-slit experiment

  • Experimental setup

  • Interference pattern

  • Conditions for constructive interference

  • Conditions for destructive interference

  • Equation for path difference

  • Example calculation of path difference

  • Recap

  • Summary and key takeaways