1. Why wave optics matters
Wave optics explains many phenomena that ray optics cannot – such as interference, diffraction, and polarisation. These ideas are not just theoretical; they form the backbone of several technologies and scientific tools used every day.
2. Applications based on interference
Interference occurs when waves overlap and add or cancel out. This principle is used in many precision devices.
2.1. Interferometers
Michelson and Fabry–Perot interferometers use interference to measure extremely small distances, refractive index changes, and wavelengths. They are essential in optical labs and scientific research.
2.2. Thin film interference
Thin layers like oil films and soap bubbles create colourful patterns due to interference. Engineers design anti-reflection coatings using the same idea so that reflections from surfaces cancel out and transmission increases.
2.3. Optical testing
Interference helps check the quality of lenses, mirrors, and optical surfaces with high accuracy. Irregularities appear as fringe distortions.
3. Applications based on diffraction
Diffraction is used when separating or analysing light. When light spreads through tiny openings or interacts with closely spaced structures, patterns appear that contain detailed information.
3.1. Diffraction gratings
Diffraction gratings separate light into its component wavelengths with high precision. They are used in spectrometers, lasers, and astronomical instruments.
3.2. CD/DVD surfaces
The fine tracks on CDs and DVDs act like natural diffraction gratings. When light reflects off them, it produces rainbow-like patterns.
3.3. Optical resolution
Diffraction limits the resolution of optical instruments like telescopes and microscopes. Wave optics helps determine the smallest detail these instruments can distinguish.
4. Applications based on polarisation
Polarisation filters out unwanted vibrations of light. This has many practical uses in daily life and in scientific instruments.
4.1. Polarised sunglasses
Sunglasses use vertically oriented polaroid sheets to block horizontally polarised glare from roads, water, and glass surfaces.
4.2. LCD screens
Liquid crystal displays (LCDs) use polarisation to control brightness. Light passes through multiple polarisers and liquid crystal layers to form images.
4.3. Stress analysis
Transparent plastics under stress change the orientation of polarisation. Using polarised light, engineers study how forces act inside materials.
4.4. 3D movie glasses
Each lens in a 3D glasses pair passes differently polarised light. Each eye receives a unique image, which the brain combines to create depth.
5. Applications based on coherence
Coherent light (light with constant phase difference) is essential in many modern technologies.
5.1. Lasers
Lasers are highly coherent sources used in communication, data storage, surgery, measurement, and cutting tools.
5.2. Holography
Holograms are created using the interference of coherent laser waves. The resulting 3D images are used in security labels, art, data storage, and imaging.
5.3. Fibre optics
Optical fibres rely on interference effects and total internal reflection to transmit signals with minimal loss, supporting high-speed communication networks.
6. Wave optics in scientific instruments
Wave behaviour is central to many advanced instruments:
- Telescopes (diffraction limits resolution)
- Microscopes (interference and resolution limits)
- Spectrometers (use gratings for wavelength measurement)
- Polarimeters (measure rotation of polarised light)
7. Wave optics in everyday life
Wave effects appear all around even without specialised equipment:
- Iridescent colours in soap bubbles and oil films
- Colour patterns on CD/DVD surfaces
- Brightness variations in thin glass layers
- Blue sky and red sunsets (due to scattering, a wave phenomenon)
8. Why wave optics is important
Wave optics connects natural phenomena with technology. Understanding interference, diffraction, and polarisation allows us to design better optical devices, improve communication systems, and analyse materials with high precision.