Speed of Light vs Speed of Sound
As seen in the previous section, the speed of sound is 340 ms−1 in air. How does this compare to the speed of light ?
In the previous section, it was assumed that light travelled Instantaneously from place to place. This is not the case! Light travels incredibly quickly, but does have a fixed speed:-
Speed of Sound = 340 m s−1
Speed of Light = 300,000,000 m s−1 or 3x108 m s−1
As can be seen, light is much much faster than sound and over short distances can be assumed to be instantaneous.
Over large distances, however, the speed of light does have an effect.
For instance, it takes 8 minutes and 20 seconds for light from the Sun to reach Earth.
Law of Reflection
When a wave 'hits' an object, the wave can change direction and 'bounce off' the object. This is known as Reflection.
There are two types of Reflection:-
1. Mirror Reflection - If the object has a very smooth surface, then all of the light is Reflected in the same way, making a mirror image.
2. Diffuse Reflection - If the object has a rough surface, then each ray of light will be Reflected in different directions, scattering the light. This is how most objects Reflect light.
When light hits a mirror, the ray of light is Reflected from its surface. The diagram below shows an example of this:-
θi = Incident angle (angle going in) in degrees.
θR = Reflected angle (angle coming out ) in degrees.
In Optics, all angles are measured from the same place, a line called the normal. This is a line at a right angle to the surface of the mirror. Never measure an angle from the mirror itself.
By experiment, we can show that:-
" For a mirrored surface, The angle of incidence of a ray of light is equal to the angle of Reflection."
This is known as the law of Reflection.
If the mirror is curved instead of flat (plane), then an unusual effect can be seen. Each part of the curved surface acts as a tiny plane mirror, following the law of Reflection. With the right shape, all of the light hitting the mirror will be focused to a single point.
This is how satellite dishes work. By Reflecting the signal all to the same point, the signal will be made stronger:-
You would use your artistic skills to create images and take photos and videos of medical conditions and treatments. Your images would be used to train healthcare staff and to support medical research.
You’d create visual records of the care that patients receive. You’d make materials for medical teaching and research.
You would record a patient's condition using a digital camera or video. You’d take photographs so that medical staff can see the effectiveness of operations and treatments over a period of time.
Using specialist equipment and techniques, you’d capture 3-D images of structures like the eye, and record specific procedures.
For some jobs you would also; do forensic photography, taking photos of non-accidental injuries, copy evidence from slides and x-rays, do bereavement photography, taking photos for grieving family members.
Training to be an Illustrator
A Career as a Medical Illustrator
Salary: from £22,000 to £55,000 per year
Illustrator working hours: 37.5 hours a week, Monday to Friday. You may sometimes need to be available for on-call duties and overtime. Job-sharing and part-time hours may also be possible.
Typical entry requirements: You would need a degree (SCQF level 9/10) in Photography followed by Postgraduate Certificate in Clinical Photography (SCQF level 11).
Certificate (SCQF level 7) or Higher National Diploma courses (SCQF level 8) with National 4/5 qualifications and one to two Highers or equivalent qualifications.
Entry to a degree (SCFQ level 9/10) requires National 5 qualifications and a minimum of four Higher or a relevant HNC/HND.
To enter a postgraduate qualification (SCFQ level 11) will usually require a relevant degree. There are no postgraduate courses in Scotland
Medical illustration is a small and specialised field and there is often a lot of competition for vacancies.
Working with technology
Attention to detail
Refraction is the process by which a ray of Light changes direction (refracts) when passing between two different mediums (materials).
This direction change is caused by the light slowing down as it passes into the denser medium.
How to label Optics diagrams
The following diagram shows how to label all optics diagrams.
The most important line to draw on these diagrams in the Normal, a line drawn at right angles to the surface, which all angles are measured from.
The above diagram shows how the path of light is refracted by the rectangular block.
The diagram shows:-
1. Angle b is equal to angle c (they form a geometrical "Z angle").
2. Angle a is equal to angle d (as long as only two media are involved).
This is because:-
When the wave enters the more dense medium it slows down and is refracted towards the normal.
When the wave enters the less dense medium it speeds up and it is refracted away from the normal.
In the rectangular block, refraction occurs twice, but in a semi-circular block refraction occurs only once. This is because the light entering the curved side of the block enters along the normal, so no refraction occurs. Refraction only occurs at the plane glass boundary.
When a ray of white light passes through a Triangular Prism, the ray is refracted twice. The overall effect of these refractions is to cause the white light to be dispersed. This causes a spectrum to be observed.
As an Optometrist, you would examine people’s eyes to check their vision and decide if they need glasses or contact lenses. You’d also look for defects, injuries and ill health.
Using your knowledge of eye diseases, if you detect abnormalities - including conditions such as diabetes and high blood pressure - you would refer the person to specialists or ophthalmologists (eye surgeons).
You’d need to be able to work with precision and understand mathematical and scientific information. It would be important to keep up to date with new techniques and instruments.
Some people may be nervous so you’d need to put them at ease. You may need to carefully and clearly explain the process and instructions, especially with children.
A Career as an Optometrist
Salary: from £31,000 to £88,000 per year
Optometrist working hours: 37 and 40 hours a week, which may include some evening shifts. Part-time work is also available.
Typical entry requirements:You need an honours degree in optometry (SCQF level 10), a Certificate of Clinical Competency and/or registration with the General Optical Council (GOC).
To enter a optometry degree (SCQF level 9/10) at Glasgow Caledonian University requires National 5 qualifications and a minimum of five Highers at AABBB.
Developing a plan