Science 8 – Physical Science Optics Chapters 4-6

4.2 Properties of Visible Light Science 8 – Physical Science - Optics

Demo - Prism What do you observe? Why? gallery.hd.org

Science 8 – Physical Science Optics Chapters 4-6

The Wave Model of Light Scientists often use models to help represent something or to understand it better so we can make predictions. The wave model of light says that “light is a type of wave that travels through empty space and transfers energy from one place to another.”(pg. 145) kidsgeo.com

Refraction of a Wave As water approaches the shore, the direction of the wave changes. This is called refraction: “Refraction is the bending or changing direction of a wave as it passes from one material to another.” (pg. 145) Student Demo meted.ucar.edu

Refraction of Light The wave model of light says that light behaves like a wave. Therefore light also refracts when it enters a new medium. So what happened with the prism?prism chemicalparadigms.wikispaces.com

The Colours of the Rainbow White light (from the sun, or the overhead projector) is made up of many different wavelengths. These wavelengths go at different speeds when they enter a new medium. Some of them will “slow down” more than others and so they get separated and we observe colours.

Rainbow Formation Look at Figure 4.11 on pg Rainbows are formed in the same way. The white light enters the water droplet and the different wavelengths separate out showing us the different colours. webecoist.com

ColourColour and Reflection math.ubc.ca

Reflection and Absorption “Reflection occurs when a light wave strikes an object and bounces off.” (pg. 148) The colours that we see result from some wavelengths of light being absorbed and others being reflected. Red, Blue, and Green are the primary additive colours. All other colours can be made by combining those. colourtherapyhealing.com

4.3 Light and the Electromagnetic Spectrum Science 8 – Physical Science - Optics

Demo – Seeing the Invisible

Radiant Energy The Sun emits, or radiates, energy in the form of different waves. This energy is called radiant energy. In these waves, electrical and magnetic fields vibrate. Therefore it is called electromagnetic radiation. space.about.com

The Electromagnetic Spectrum The light we see is referred to as the visible spectrum. This is only a small part of the electromagnetic spectrum. There are other waves that have larger and smaller wavelengths than the visible spectrum. lcse.umn.edu

Figure 4.20

Radio Waves Radio waves have the longest wavelength and the lowest energy and frequency compared to all other EM waves. Radio waves are commonly used for radio and television broadcasting (Fig. 4.21) as well as MRI imaging. ecrc-pt.com businessweek.com

Microwaves Microwaves have shorter wavelengths and higher frequencies than other radio waves. Microwaves are strongly absorbed by water particles so are used in microwave ovens to heat foods that contain water. They are also used in telecommunications and radar. renthire.com mydreamcourse.co.za atmos.washington.edu

Infrared Waves Infrared waves have wavelengths just longer than the visible colour red. Infrared waves are used in remote controls and to read CD-ROMs. Infrared radiation is also known as heat radiation because everything with some heat energy emits infrared waves. useit.com commons.wikimedia.org imaging1.com

Ultraviolet Waves This type of electromagnetic radiation has a shorter wavelength and therefore higher frequency and energy than visible light. It enables your body to produce vitamin D, which is needed for healthy bones and teeth. UV waves are used in forensic science to study finger prints. They also kill bacteria in food, water, and medical supplies. Overexposure can lead to sunburn, skin cancer, and damage to the eye.

X Rays X rays are commonly used to photograph teeth and bones. Other uses include airport security and inspection of the inside of machines. hahahaimontheinternet.com dvice.com

Gamma Rays Gamma rays are the shortest wavelength and highest frequency and energy wave. Gamma rays are formed in nuclear reactions. They are used in radiation therapy to kill cancer cells. stfc.ac.uk