Light

Light

•Is a form of energy•Behave as an electromagnetic wave•Have both electrical and magnetic properties•Can travel through empty space•Are made up of tiny particles or energy called photons•Unless disturbed, photons travels in straight lines.

Light

Electromagnetic Spectrum

• Range of waves or small parts of light waves that make a electromagnetic spectrum( Large band of waves)

• Energy of a wave is related to its wavelength and its frequency.

Visible Light Waves

*The longer wavelength, lower frequency regions

*The shorter wavelength, higher frequency regions

The Electromagnetic Spectrum

Electromagnetic waves

• Visible light waves are the only electromagnetic waves we can see

• Each color has a different wavelength• Red has the longest wavelength • violet has the shortest wavelength. • When all the waves are seen together, they

make white light.

Creating a rainbow.

What are electromagnetic waves ?

• Radio waves• microwaves, • Infrared• Ultra Violet• x-rays• TV• radio transmissions • Gama rays

Radio Communication cont’d.

• Television– Sound by FM; picture components by AM

• Telephones– Microphone converts sound waves into an

electrical signal– In cell phones, current creates radio waves

transmitted to and from a microwave tower– Cordless and cell phones are transceivers that

transmit one radio signal and receive another from a base unit

• Global Positioning System (GPS)– Uses multiple satellites, monitoring stations, and

receivers to determine location

Electromagnetic Spectrum cont’d.

• Radio waves– Longest wavelength, lowest frequency, sound;

radar; magnetic resonance imaging (MRI)• Microwaves – Communication, microwaves interfere with the

water molecules in food causing more friction• Infrared– Transmits thermal energy

• Visible Light– Frequencies detected by the nerves in the eyes ;

blue—shortest wavelength; red—longest wavelength

• X-rays– Can travel through matter and

produce images– Dense parts of the body

absorb more than the soft parts of the body

– Medical diagnosis• Gamma rays– Highest frequency, lowest

wavelength– Medical treatments to kill

diseased cells, but also damages healthy cells

Light waves• a ray of light passes from one medium to another,

it bends• Depending of the new medium the light will travel

faster or slower. • the medium in which the light travels slower( in this case the first one) is called the denser

medium.

Rarer medium and Denser medium

• When a ray of light enters a denser medium, it is bent towards the normal.

• When a ray of light enters a rarer medium, it is bent away from the normal.

•When a ray of light strikes a plane mirror, the light ray reflects off the mirror. • Reflection involves a change in

direction of the light ray

Light WavesLight Waves

Incident, Reflection and Normal

• incident ray -the ray of light approaching the mirror • reflected ray -The ray of light which

leaves the mirror • normal line -At the point of incidence

where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror;

The angle of incidence

• is the angle between this normal and the incident ray

The angle of reflection

• is the angle between this normal and the reflected ray.

The Laws of reflection:

• - The angle of incidence is equal to the angle of reflection • - The incident ray, the normal, and

the reflected ray are coplanar(lying or acting in the same plane )

Three types of materials that affect light differently.

• Opaque- Block the light• Translucent-May allow some light to

pass Ex: Stained glass.• Transparent-allow the light to pass