Waves and the Electromagnetic Spectrum Ms. Twardowski 8 Tan Dover Central Middle School

Waves  Waves are a means by which energy is transported from one region to another.

Waves  Energy is carried from one point to another through the action of invisible waves!  DID YOU KNOW that invisible waves of energy are bouncing off us, passing through us, and being absorbed by your body EVERY second of EVERY day?!

Parts of a Wave  Crest – the top part of the wave.  Trough – the bottom part.  Wavelength – the distance from crest to crest on a wave.  Frequency – how many ‘crests’ pass by a certain point per second.

Frequency  The higher the frequency number the faster the wave moves.  The faster the waves moves, the more energy it carries.  Some waves are dangerous and can cause cancer, damage your skin and eyes, and even cause death!

Waves  All waves have a source…the SUN!  The sun transforms energy into forms that can be carried by waves.  WAVES ARE NOT MATERIAL OBJECTS! You can’t touch them or see them. They have NO mass!

Waves  Waves are vibrations that transport energy.  Sometimes waves need these vibrations of particle in the object to move.  Some waves can travel without the need for vibrations in particles.

Mechanical Waves  There are two categories of waves. One is Mechanical.  Mechanical Waves NEED particle vibrations to move energy. (Therefore, anything that is a mechanical wave would NOT work in space!)  They carry KINETIC energy (KE)

Some type of Mechanical Waves  Sound waves (hearing, listening to music, etc.) –Audible waves (20Hz-20,000Hz) – waves you can hear. –Infrasonic waves (too slow to activate your hearing. Below 20Hz) –Ultrasonic waves (vibrate too fast to be heard by “humans”. Above 20,000Hz)  Earthquakes and tsunamis

Electromagnetic Waves  Do NOT need particles vibrations to be transported  CAN work in the empty vacuum of space!  Carry ELECTRIC and MAGNETIC energy (EM)

The Electromagnetic Spectrum  There are seven (7) types of EM Waves: –Gamma rays (fastest and DANGEROUS) –X-rays –Ultraviolet (UV) radiation –Visible Light (how we see) –Infrared radiation (IR) –Microwaves –Radio waves

Organisms and waves  Animals that can hear and produce infrasonic waves: elephants, pigeons, octopus, squid, etc.  Animals that can hear ultrasonic waves: bats, dogs, cats dolphins, etc.  Animals that can see UV light: bees, butterflies, spiders (most mammals CANNOT see UV light).  Animals that can see IR: snakes, mosquitoes, most predators.

How important is energy transported by waves?  The energy that is carried by waves is critical to life on Earth (see paper on Elmo. Lab #12, page 7).

Review  What is the source of all energy? (Answer, please!)  Name the parts of a wave.  Name a type of mechanical wave.  Name at least 3 electromagnetic waves.  Which EM waves enable us to see?

How We Hear and How We See.  Homework: Due the next time you have science.  Read How We Hear and How We See.  Take notes on both papers.  Draw AND label parts of the ear and eye. (You can trace if you want).