3B Scientific UE4030100 Diffraction on an Individual Slit User Guide
- June 7, 2024
- 3B Scientific
Table of Contents
3B Scientific UE4030100 Diffraction on an Individual Slit
Product Information
- Diffraction of light by a single slit can be described as the superposition of coherent wavelets which spread out from the illuminated slit in all directions. Constructive or destructive interference occurs depending on the angle of propagation, leading to light and dark bands observed on a screen.
- This experiment investigates diffraction by single slits of various widths and different wavelengths of light. It also demonstrates complementary diffraction patterns between a single slit and an opaque object of the same width.
Specifications
- Product Code: UE4030100
- Product Name: Diffraction by a Single Slit
- Objective: Demonstrate the wave nature of light and determine the wavelength
Product Usage Instructions
- Set up the required apparatus including the Laser Diodes, Optical Bench, Optical Riders, Adjustable Slit, and Holder for Diode Laser.
- Ensure proper alignment of the components according to the experiment setup guidelines.
- Adjust the slit width and distance to the screen as needed for the experiment.
- Observe the diffraction pattern on the screen and measure the distances between dark bands for analysis.
- Calculate the wavelength based on the measured distances using the provided formulas and principles.
Frequently Asked Questions
Q: What is the significance of Huygens' principle in this experiment?
A: Huygens' principle explains the wave nature of light and how coherent wavelets contribute to diffraction patterns by a single slit through constructive and destructive interference.
Q: How can I determine the wavelength of light in this experiment?
A: The wavelength can be calculated based on the distance between adjacent dark bands of the interference pattern using the provided formulas and experimental measurements.
Q: Why are diffraction patterns of single slits and opaque objects complementary?
A: According to Babinet's principle, diffraction patterns of complementary objects are identical outside the unaffected beam, leading to complementary diffraction patterns between a single slit and an opaque object of the same width.
EXPERIMENT PROCEDURE
- Investigate diffraction by single slits of various widths.
- Investigate diffraction by a single slit for light of differing wavelengths.
- Investigate diffraction by a single slit and by an opaque object of the same size (Babinet’s principle).
OBJECTIVE
Demonstrate the wave nature of light and determine the wavelength
SUMMARY
- Diffraction of light by a single slit can be described as the superposition of coherent wavelets which, according to Huygens’ principle, spread out from the illuminated slit in all directions.
- Depending on the angle along which they propagate, the wavelets cause either constructive or destructive interference.
- If the width of the slit and the distance to the screen are known, then the wavelength can be calculated based on the distance between adjacent dark bands of the interference pattern.
REQUIRED APPARATUS
Quantity
| Description|
Item Number
---|---|---
1| Laser Diode, Red
Laser Diode, Red 115V
| 1003201 or
1022208
1| Laser Module, Green| 1003202
1| Optical Bench K, 1000 mm| 1009696
2| Optical Rider K| 1000862
1| Adjustable Slit K| 1008519
1| Holder K for Diode Laser| 1000868
BASIC PRINCIPLES
- Diffraction of light by a single slit can be described as the superposition of coherent wavelets which, according to Huygens’ principle, spread out from the illuminated slit in all directions.
- This superposition leads to either constructive or destructive interference depending on the angle. Beyond the slit, a system of light and dark bands can be observed on a screen.
Where the wavelets cancel – i.e. where the bands are darkest – it can be seen that for every wavelet from one half of the slit, there is another wavelet from the second half which interacts with it in such a way that the combined amplitude is reduced to a minimum. This happens when the path difference Δ sn between the beam through the middle of the slit and a ray from the edge is precisely an integer multiple n of half the wavelength λ:
The regions of maximum darkness are symmetrical about the primary ray (see Fig. 1). Their distance from the primary ray, as measured in the plane of observation is as follows:
L: Distance between slit and plane of observation For a small angle, the following is therefore true:
- A slit and an opaque obstruction of the same size and shape are considered complementary diffraction objects. According to Babinet’s principle, the diffraction patterns of both objects, outside of the “unaffected” beam, are identical. The diffraction minima in both patterns are therefore in the same place.
- In this experiment diffraction by single slits of various widths is investigated, along with diffraction of different wavelengths of light. Moreover, it will be shown that diffraction by a single slit and by an opaque object of the same width results in complementary diffraction patterns.
EVALUATION
The brightness is greatest in the direction of the primary ray. The value Δ
can be determined as the gradient of the straight line graph when the
distances xn are plotted against n. Since Δ is inversely pro portional to the
width of the slit b, the quotients Δ/L can be plotted in a graph against 1/b
and the wavelength λ is then determined as the gradient of the graph of these
measurements.
Fig. 1: Schematic diagram of diffraction of light by a single slit (S: Slit, b: Width of the slit, E: Plane of observation, P: Primary beam, L: Distance of observation screen from slit, x2: Distance of second minimum from centre, α 2: Direction of observation for second minimum, Δ s2: Path difference between ray through centre and ray from the edge).
Fig. 2 Calculated and measured intensities for diffraction from a slit of width 0.3 mm with light of wavelength λ = 650 nm and λ = 532 nm.
Fig. 3: Separations xn as a function of diffraction order n for various widths of slit b where λ = 650 nm.
Fig. 4: Quotient of relative separation of minima Δ and distance L as a function of width of slit 1/b.