Physical Science: Optics Outcome C1

Properties of waves –Light is a type of electromagnetic energy which travels in a wave at the speed of 300, 000 km/s –A wave is the result of a vibration that transfers energy from one location to another

Properties of waves –A wave has: 1. Crest – The peak (highest position) of the wave 2. Trough – The lowest position of the wave 3. Wavelength – The distance between two adjacent crests, OR two adjacent troughs

Properties of waves –A wave has: 4. Amplitude – the distance above or below the resting position 5. Frequency – the number of wavelengths in a given time Frequency is measured in Hertz (Hz) which means number of cycles per second

Properties of waves –The higher the frequency of a wave, the higher the energy it has –The lower the frequency of a wave, the lower the energy it has

Properties of waves –2 types of waves: –1. Compression waves – slinky –These waves move back and forth along the same direction the wave travels –2. Transverse waves – waving rope –These waves move perpendicular to the direction the wave travels –Waves move energy, not matter (substance)

Properties of waves –Waves can travel in a medium or in the air – A medium can be anything that is a liquid, solid, or gas or a combination of these –For example: Think of when you shine a light into a pond

Properties of waves – Refraction – When waves change direction slightly because it has travelled from one medium, into another – Reflection – When waves “bounce off” a surface and changes direction

Physical Science: Optics Outcome C2 – Properties of visible light

Properties of Visible light 1. Light is a form of electromagnetic energy –It is part of the electromagnetic spectrum

Electromagnetic spectrum –What is a spectrum? –“Range” of energies –Microwaves, radio waves, x-rays

Properties of Visible light 2. Visible light is also called White light – White light is made up of the visible spectrum –The Visible spectrum are all the colours that are visible to our eye The colours: Red, Orange, Yellow, Green, Blue, Indigo, Violet The correct mixture of all the colours will produce white light

Properties of Visible light 3. Light travels in straight lines 4. Light travels in waves 5. Light waves will reflect and refract

Properties of Visible light –Different colours of the visible spectrum have different wavelengths –Longer wavelengths appear Redder –Shorter wavelengths appear Bluer

Properties of Visible light – White light can be separated into a spectrum of colours, when passed through a triangular prism –This separation of light is what we see when there is a rainbow

Properties of Visible light – Refraction of light – the bending or change in direction of light –this happens when light travels at an angle and passes from one medium to another. –If the medium causes the light wave to slow down, it will bend – Longer wavelengths will bend less – Shorter wavelengths will bend more

Properties of Visible light – Reflection of light – when a light wave hits a surface, and bounces off –We see objects as specific colours because the material absorbs all the colours except for the one we see –If no colours are reflected, an object is black. If all colours are reflected, an object is white

Properties of Visible light Ex: An orange is orange coloured because it reflects the colour orange, and absorbs all the other colours Ex: Mr. Gary’s hair appears black because all the colours are being absorbed and not reflected.

Sources of light – Luminous objects are things that can emit light – Non-luminous objects are things that only reflect light – Types of light sources: – 1. Incandescence – Light coming from hot things – 2. Phosphorescence – Light emitted when phosphors release stored energy

Sources of light – 3. Electric discharge – Light created when electricity passes through gas particles – 4. Fluorescence – Light created by one object that is receiving energy from another

Sources of light – 5. Chemiluminescence – light created when chemical energy is changed into light energy

Sources of light – 6. Bioluminescence – light created by living things

Movement of light waves –Objects have different levels of transparency; they can be transparent, translucent, or opaque. – Transparent material allows light waves to pass through easily –Ex: plastic wrap, glass

Movement of light waves – Translucent material allows most light waves through, but blocks some. This results in things looking blurry. –Ex: my water bottle, smudged glass, clouds – Opaque objects block all light waves from passing through –ex: rocks, wood, bricks