Light & The EM Spectrum

What is Light ? 

Light is a type of transverse wave, made from Electric and Magnetic fields. 

Light travels at 300,000,000 m/s and nothing can go faster than this.  

Light waves can pass through solids, liquids and gases. They can even travel through a vacuum. 

Law of Reflection 

When light 'hits' an object, it 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:-

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. We 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. 

Curved Reflectors

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.

Refraction

Refraction is the process by which a ray of Light changes speed as it moves between materials of different density. This can cause a change in direction if the beam of light enters the object at an angle.

Semi-Circular Block

In a semi-circular block refraction appears to occur only once. This is because the light entering the curved side of the block enters along the normal, so no change in direction occurs (But it still refracts- i.e. slows down). At the flat side, the beam hits at an angle, so refraction and a change of direction occurs.

Triangular Prism

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 into the colours of the rainbow. This causes a spectrum to be observed. 

Rainbows

If the sun is behind you, with rain in front of you, a rainbow can be seen. A rainbow is an optical effect caused by light being refracted and relfected inside raindrops : 

The Electromagnetic Spectrum 

Visible light is only actually a very small section of a much larger spectrum - the Electromagnetic spectrum. 

The video below gives an introduction to light and the EM Spectrum : 

Like light, all sections of the Electromagnetic spectrum : 

• Are made up of changing electric and magnetic fields.

• Travel at the same speed (300,000,000 m/s).

• Can travel through a vacuum.

•  Can be reflected.

• Can be refracted.

The only difference between visible light and the rest of the EM Spectrum is the energy of each section (which varies with the Frequency of the light).

The table below gives key information about each part of the EM Spectrum:-

As a Telecoms Engineer, you would set up and look after broadband, mobile phone and landline telephone networks. You would also work on satellite, digital TV and fibre optic systems.

The size of each job would vary. You might set up a large corporate network one day and a home satellite system the next.

This job can be dangerous, and you may sometimes have to work at heights. You would have to follow health and safety guidelines carefully at all times.