Why is wave optics needed

The information on these discs are read by a computer in the form of binary data. First, a laser beam is shot at the disc. If the beam hits a land, it gets reflected back and is recorded as a value of 1. If the beam hits a pit, it gets scattered and is recorded as a value of zero. Early Version of an Optical Disc : In this early version of an optical disc, you can see the pits and lands which either reflect back light or scatter it.

These microscopic pits and lands cover the entire surface of the disc in a spiral path, starting in the center and working its way outward. The data is stored either by a stamping machine or laser and is read when the data is illuminated by a laser diode in the disc drive. The disc spins at a faster speed when it is being read in the center track, and slower for an outer track.

This is because the center tracks are smaller in circumference and therefore can be read quicker. These pits also act as slits and cause the light to be diffracted as it is reflected back, which causes an iridescent effect. This explains the rainbow pattern that you see on the back of a CD, as shown in.

Compact Disc : The bottom surface of a compact disc showing characteristic iridescence. Privacy Policy. Skip to main content. Wave Optics. Search for:. Applications of Wave Optics. Enhancement of Microscopy Microscopy helps us view objects that cannot be seen with the naked eye. Learning Objectives Compare optical and electron microscopy. This technique has many limitations but can be enhanced in various ways to create more contrast.

The transmission electron microscope TEM sends an electron beam through a thin slice of a specimen. The electron is then transmitted onto photographic paper or a screen. Since electron beams have a much smaller wavelength than traditional light, the resolution of this image is much higher. The scanning electron microscope SEM shows details on the surface of a specimen and produces a three-dimensional view by scanning the specimen.

The Spectrometer A spectrometer uses properties of light to identify atoms by measuring wavelength and frequency, which are functions of radiated energy. Learning Objectives Compare design and function of early and modern spectrometers. Key Takeaways Key Points The source is placed in front of a mirror, which reflects the light emitted from that object onto a diffraction grating. Early forms of spectrometers were simple prisms, but modern spectrometers are automated by a computer and can record a much broader range of frequencies.

Spectrometers are used in spectroscopy. Key Terms incandescence : Incandescence is the emission of light visible electromagnetic radiation from a hot body as a result of its temperature. The Michelson Interferometer The Michelson interferometer is the most common configuration for optical interferometry. Learning Objectives Explain how the Michelson interferometer works. Key Takeaways Key Points Interferometry refers to techniques that use superimposed waves to extract information about the waves.

Michelson interferometer works by splitting a beam of light into two paths, bouncing them back and recombining them to create an interference pattern. To create interference fringes on a detector, the paths may be different lengths or composed of different materials.

The best known application of the Michelson interferometer is the Michelson-Morley experiment, the unexpected null result of which was an inspiration for special relativity. Key Terms special relativity : A theory that neglecting the effects of gravity reconciles the principle of relativity with the observation that the speed of light is constant in all frames of reference.

Michelson Interferometer : A Michelson Interferometer. LCDs Liquid crystal displays use liquid crystals which do not emit light, but use the light modulating properties of the crystals. Learning Objectives Explain how liquid crystal displays produce images and discuss their benefits and deficiencies.

Key Takeaways Key Points LCDs use an electric field to arrange the liquid crystals into the desired pattern, and then pass light through these layers to produce an image on the screen. LCDs can be used to display an arbitrary image made up of tiny fixed pixels, or can be used to display a fixed image, as in on a digital clock.

A twisted nematic display is the most common LCD in use. Snell's laws proof using Huygen's principle Opens a modal. Constructive and Destructive interference Opens a modal. Young's double slit experiment. Young's double slit introduction Opens a modal. Young's double slit equation Opens a modal.

Young's double slit problem solving Opens a modal. Fringe width in Young's double slit experiment Opens a modal. Double-slit experiment: fringe widths one wavelength. Double-slit experiment: overlapping fringes two wavelengths. Modified Young's double slit experiment.

The sections are as follows What did we see in the introductory slide show? This list is intended to indicate some examples of ideas in optics and waves, and to describe the path we will be taking in the subject during the forthcoming lectures.

The compact disc player - Our prime example of the modern relevance of optics - and the excuse to get some musical backing. This is why the sky looks blue to us. Also, when the sun's rays propagate through a long path in the atmosphere more blue light has been scattered out of the beam than red, and so more red than blue remains Rayleigh scattering. Blue skies - Some of the sunlight travelling through the atmosphere is scattered towards the earth; blue light is scattered more strongly than red, therefore White snow - Why is snow white?

Rainbows - You have all seen them, but how is the white light split up into the arcs of different colours that we see in the rainbow? See the material on rainbows in the ray optics section to learn more. Various colours - What is "colour"? How much is physics, and how much is psychology and physiology? Other colours such as brown, grey, purple, etc, are as much psychological and physiological in origin as physical. Prism and Refraction - "White" light is composed of many different wavelengths, which we can separate by using, for example, a prism.

Spectacles, cameras, - The idea of the lens and image formation are important for telescopes, binoculars many optical instruments, and we shall spend some time developing the theory needed to predict the behaviour of light and lenses. Cats eyes - What is happening in our cat and on the road to give strong reflections back towards us?

Some interesting ideas in refraction and reflection here. Timepieces - The pendulum clock and the "quartz" watch both function due the well-defined period associated with an oscillator. Although the sizes are very different, much of the physics is the same. Water waves - Water waves or ripples carry energy from one place to another. How can we describe them? Sirens - The shift in frequency that we hear as it goes past is due to the Doppler effect. We will come back to the same ideas later using light.

Musical Instruments - The standing waves set up in air columns or on strings are the basis of music-making.