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