Optics is the study of light and its uses. "Light" is electromagnetic
radiation which can be detected by our eyes, ie electromagnetic radiation with wavelengths
in the range ~400 nm - 700 nm (though often very similar ideas apply beyond both ends of
this wavelength range). In this lecture course we will look at basic ideas of light
propagation, geometrical optics (imaging, etc), interference and diffraction of light, and
some of the many uses to which light is put. Far from being just an "old"
subject, optics is becoming increasingly important as more and more use is being made of
lasers and optoelectronics in industry and society. We will look at various examples
including laser-based remote sensing, optical communications, laser-based length
measurement, and optical data storage (the CD). The last topic is the one which has
brought lasers, precision optics, and optoelectronics into many households; we will be
using this example throughout the course to illustrate the various optical phenomena that
we shall be attempting to explain.
Course Structure
A more detailed breakdown is given on the home
page for the course. The sections are as follows:-
- Introduction - The relevance of optics and the nature of light.
- Geometrical Optics - Snell's law, total internal reflection, and examples;
- Imaging, the thin lens formula, and examples of optical instruments;
- Oscillations and Waves - Oscillations and simple harmonic motion; travelling waves;
Doppler effect; linear superposition and beats; reflections; standing waves.
- Wave Optics - Wave description;
- Two beam interference - Young's slits and Michelson's interferometer;
- Multiple beam interference
Slide Show
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.
Red sunrise/sunset - Blue light (short
wavelength) is scattered more strongly than red (longer wavelength), as the amount of
scattering depends on l-4. 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? See, for example, "Clouds in a
Glass of Beer" by Craig Bohren.
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? The colours of the spectrum are directly related to
the wavelength of the light, red at ~630 nm, orange as in sodium street lights at 590 nm,
yellow around 570 nm, green around 530 nm, blue around 480 nm. 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.
Quantum Waves - We will leave a good treatment of quantum mechanics to
Physics 1B, but let us note that many of the ideas of classical waves transfer to the
complexities of the quantum world.
Colours in oil spills and mega-bubbles -
Where do these colours appear from? We will need to use ideas about light as a wave, and
how waves can interfere with each other, in order to explain the origin of these patterns.
Hovering spectra - Produced by shining a spotlight through a special
effects filter - a diffraction grating in fact. We will need to look at light as a wave
again here, and will show how these effects can be used to separate light of different
wavelengths in spectroscopy (terrestrial or astronomical), and to colour certain insects.
Optical Fibres - Application of basic ideas of reflection and refraction show
that light can be guided along transparent fibres. This may be used for illumination or
for optical communications. Optical communications? If you telephone anyone more than a
few tens of miles away you are likely to be using optical fibres, and if you use the
University computers, that whole network is linked together using pulses of light speeding
through a loop of fibres around St Andrews. The "light" that is chosen for use
has a long wavelength - due to Rayleigh scattering again. This School is currently
leading a 10.5 million pound research
collaboration looking at how to get even faster data transfer across optical
communication networks.
Lasers - A flourishing research field in
this school, and a technologically important topic. The laser is a prime example of the
modern use of optics, with applications in material processing, optical communications,
optical data storage, medicine, warfare, science, metrology, and reprographics.
Recommended Books
Most of the fundamental ideas in waves optics are well covered in the
general textbooks that have been recommended to you (Halliday, Resnick, & Walker;
Ohanian). Books specifically on optics that you may find useful reading include
- Lothian, "Optics and its Uses"
- Longhurst, "Geometrical and Physical Optics"
- Jenkins and White, "Fundamentals of Optics"
- Hecht, "Optics"
All are on reserve in the departmental library. Longhurst is my
favourite, but Hecht is the one that is currently recommended for purchase for the Honours
course on Optics.
Electronic Information and Simulations
I will be using a number of computer-based simulations in this course
to try to explain what is going on. I believe that you will find them useful to
explore. In the web pages of lecture summaries you will find a number of "Java
applets" that should be able to run on most computers. These are small programs
that allow us to get you exploring some of the optics ideas. Most are from other
sites, and are acknowledged as such. Those from Lightlink have a <=Back button at
the foot of their pages - this is not a back button in the correct sense; clicking on this
will take you to the Lightlink index. Please use your browser's back button instead.
In the tutorial questions we make use of more substantial simulations,
which are available for your use in our PC Classroom. The tutorial questions printed in
this handout are also reproduced electronically on the World-Wide-Web. These pages are
accesible from networked computers within the st-andrews.ac.uk domain. But to gain full
benefit from them, the PC Classroom here is best, as there are links from the web-pages to
the simulation programmes that are loaded on the PC Classroom network. To get to the pages
associated with this (and other) courses within the School, follow the links from the
University’s page => Academic Schools => Physics and Astronomy. Once there,
follow the links on Teaching and Courseware. Special sessions will be run in first week to
introduce students to the PC Classroom, Windows NT, the Web, and the use of the
simulations. As well as this being useful for your study of physics, experience of
computers is now almost a pre-requisite for many careers.
The physics and mathematics of wave motion underlie many important
phenomena. The water wave on the sea, the vibration of a violin string, and the quantum
mechanical wave associated with an electron can all be described in a similar way. Light
too, often displays properties that are wave-like. We will start the course looking at
"ray" optics, but then pause for a general treatment of waves of all types. We
will start this waves section by reviewing ideas of oscillations and simple harmonic
motion, and go on to look at the physics of travelling and standing waves. We will apply
these ideas to various types of wave, and see how all-pervading this topic is in physics.
We will then be in a position to consider a number of phenomena in which the wave
properties of light are important. 
I strongly recommend that you review the
material in each lecture as soon as possible, and certainly before the next lecture. As
you can see from the course structure, many topics build on ideas presented before. Again
I stress, if you have queries, please ask; that is what your lecturers are here for.
Bruce