LIGHT

Light is an electromagnetic wave similar to radio waves. It has wavelength and frequency.
It travels at 300,000,000 metres per second.
Wavelength, frequency and the speed of light are related.

Wavelength x frequency = the speed of light.

Different colours of light have different frequencies.

When a ray of light hits a shiny surface it is REFLECTED.
The angle of reflection equals the angle of incidence.

When light passes from one transparent material to another it is REFRACTED.(bent).

LENSES use refraction. CONVEX lenses FOCUS a beam of light to a point.

CONCAVE lenses cause the beam to DIVERGE.

The PRIMARY colours which make up white light can be separated out by a glass PRISM.

Three of the primary colours, RED, GREEN and BLUE are used in the colour television system.
By mixing them most other colours can be made.
In the next diagram, red and green make yellow, green and blue make cyan and red and blue make magenta.
White is made by using all three colours.

CLIPPERS AND LIMITERS

Clipping removes part of the positive or negative peaks of a signal or both.

Silicon diodes do not conduct until the applied voltage exceeds about 0.6 volts and only when the anode is positive with respect to the cathode.

The circuit is like a potential divider with the diode part being high resistance for voltages below 0.6 volts and low resistance above.

Fig. 1 shows the waveform into the clipper.

Fig. 2 is the output of a positive clipper and fig. 3 the output of a negative clipper.

Fig. 4 has both peaks clipped and is often used as a LIMITER where the output must not exceed 1.2 volts.