Light and the
electromagnetic
spectrum
Optics
Definition:
Optics is the study of the behaviour and
properties of light
Optical Illusions
Optical Illusions
Optical Illusions
What is Light?
Light is a form of energy (electromagnetic
radiation in the form of waves)
It is a part of the electromagnetic
spectrum
White light is composed of all the colours
of the rainbow (ROY G BIV)
Wave energy
A wave is a disturbance that transfers
energy from one point to another without
transferring matter
Properties of waves
Wavelength – The distance from one
point in the wave to the next similar point
in the wave
E.g. crest to crest, or trough to trough
Represented by the Greek letter lambda
λ
Properties of waves
Amplitude – the wave height from the rest
position of the wave to the crest or the
wave depth from the rest position to the
trough
The larger the amplitude, the more energy
it carries
The smaller the amplitude, the less energy it
carries
Properties of waves
Frequency – the rate of repetition of a
wave
For example: If the crest of a wave passes a
certain point 5 times in a second, the
frequency is 5 cycles/second.
The higher the frequency, the more energy
the wave passes along
The symbol for frequency is f, and it is
commonly measured in hertz (Hz) which is
cycles per second
Wave Diagram
Frequency and Wavelength
Frequency and wavelength have an
inverse relationship.
An inverse relationship means that as one
value increases, the other decreases.
As frequency increases, wavelength
decreases
As frequency decreases, wavelength
increases
Frequency and Wavelength
This relationship can be represented by the following formula:
v = f λwhere v represents speed, f represents frequency and λ represents wavelength
The Electromagnetic
Spectrum
Light is a form of energy and visible light is
only a tiny fraction of the energy known
as electromagnetic radiation
Electromagnetic radiation is a wave
pattern made of electric and magnetic
fields that can travel through empty
space
It ranges from the shortest gamma rays to
the longest radio waves
The Electromagnetic Spectrum
The Electromagnetic Spectrum
Radio waves
Longest wavelength, lowest frequency, lowest energy
Used for radio signals, television signals, cell phones, and satellite communications
Used in MRI medical equipment
Microwaves
Shorter wavelengths, higher frequency,
and higher energy than radio waves
In microwaves, they cause water
molecules in the food to vibrate, which
then heats the food
Used in radar to measure speed and
monitor vehicles, and in satellite
communications
Infrared waves
Shorter wavelengths than microwaves but
longer than light waves
Infrared radiation is
experienced by us as
radiant heat
Can be sensed by
special imaging
equipment for burglar
alarms, motion sensors,
and night vision
Visible light
Range between 390nm – 700nm for the
typical human eye
Ultraviolet rays
More energy, shorter wavelength, and higher
frequency than visible light
Mainly emitted by stars like our sun
Extended exposure can cause burns and lead
to cancer
Can be used
for
disinfection,
DNA analysis,
and CSI work
X-rays
High energy waves that can pass through human tissues
They cannot pass through bone, metals, or hard plastics, which makes them useful for medical imaging or security
Gamma rays
Extremely high energy waves that can pass
through human tissues
Used for sterilization and cancer treatment
Produced by neutron stars and black holes