Bell Work 10/20/15 Get a textbook, do NOT copy the question, answer in a COMPLETE SENTENCE…. 1) “What are waves?” 2) Name the 3 types of mechanical waves and describe the movement of each one. A wave is a disturbance that transfers energy from place to place. 2) Transverse: moves “up & down” Longitudinal/Compressional: moves back & forth Surface: combination of transverse & longitudinal

Waves

What is a Wave? A Wave is a disturbance that transfers energy from place to place. In order to pass it’s energy along, waves pass through a medium.(this is the material through which a wave travels). (A medium can be a solid, liquid or gas).

Not all waves need a Medium! Some waves DO NOT always need a medium, in order to pass its energy along. For example, electromagnetic waves can go through some matter such as air, water, and glass BUT do not have to have a medium to transfer their energy. They can actually travel where there is little to no air such as in outer space! This is why they can travel so fast! No obstacles! Examples include: ultraviolet waves, microwaves, x-rays, radio waves and even light waves!

Waves transfer energy, not matter Waves transfer energy, not matter. The water particles in the waves below are carrying energy but are not moving. Waves can only exist if they have energy to carry.

What causes waves? Waves are created when a source of energy causes a medium to “vibrate” A vibration is a repeated back and forth or up and down motion.

How do we classify waves? Waves are classified according to how they move. We classify waves based on the direction in which the particles of the medium vibrate compared to the direction in which the wave moves.

Types of Mechanical Waves: Longitudinal (compressional) Transverse Surface

Transverse Wave Vibrates perpendicular (at right angles) to the direction in which the wave travels. These waves move in an “up and down” motion. *Similar to popping a rope up and down)

Parts of a transverse wave: The highest point on a transverse wave is called the “crest”. The lowest point or the “valley” on the transverse wave is called the “trough”.

Longitudinal Waves Vibrate parallel to (in the same direction of) wave travel. It produces a “back and forth” type of motion. (ex: sound waves) It’s similar to pulling one end of a slinky. The wave travels through the medium from one end and back again to the other.

Parts of a Longitudinal wave… The part of a longitudinal waves where the particles are “crowded” is called the compression. The parts of the waves where they are “farthest apart’ is called rarefaction. “Compression” --Rarefaction-

Surface Waves These are a combination of longitudinal & transverse waves. They look like transverse waves, but the particles travel through the medium in circles rather than up and down. The particles create the circular movement by moving forward at the crest of each wave and by moving backwards at the trough. Now give the students the worksheet on “Diagram of a Wave”….students will have to label the parts and answer a few questions at the bottom of the sheetl.

Electromagnetic Waves Can travel through a medium AS WELL AS THROUGH SPACE!!! Keep in mind that “space” is a vacuum (in other words there is “no air” in space). Electromagnetic waves are also transverse waves when looking at how they travel.

To sum it all up!!!...... Mechanical Waves: (--must have a medium) a) Transverse (up & down) b) Longitudinal (back and forth) c) Surface (all around) Electromagnetic Waves: (can move through medium + space) ex: gamma rays, microwaves, x-rays, light, ultraviolet, infrared)

Properties of Waves….. Waves have several properties such as: a) Amplitude -------- (the height of the wave) b) Wavelength -------- (the distance between the 2 crests) c) Frequency ------ (# of waves in certain amt. of time) d) Wave speed ----- (rate at which the wave moves)

“Amplitude” The amplitude of a wave is related to its “height”. A wave’s amplitude is the maximum distance that the particles of the medium vibrate from their rest point. The rest point is the point where the particles of the medium stay where there is no disturbance.

“Wavelength” This is the distance between two crests. The shorter the wavelength the greater the amount of energy carried. The longer the wavelength the lesser amount of energy carried.

“Frequency” --is the number of waves produced in a given amount of time. The higher the frequency, the greater the amount of energy that was made. The lower the frequency, the lesser amount of energy that was made. *Frequency is measure in ___________ Low frequency Hertz High frequency

“Frequency” Is similar to the movements of a jump rope. Moving the rope quickly makes a larger number of waves. (in a given time). Moving the rope slowly makes a lower number of waves. Simulation clip on frequency and amplitude of a wave!!!

Brainpop: How stuff works video clip on waves After the videos, complete the back of the worksheet: Diagram of a Wave titled “Profile of a Wave”

Bellwork Part B 4/15/13 pg. 182 ISN Examine the diagrams below. Please compare the following: Amplitude • Wavelength • Frequency • Amount of energy Diagram 1 Diagram 2

Practice Time: See if you know the answers! The following questions were taken from last year’s TCAP practice book …. Complete them and then we will discuss the answers – Good Luck! 

*There are two BW questions! Answer: “C”

Answer: “B”

*There are two BW questions! Answer: “F”

Answer: “J”

Answer: “G”

Answer: “A”

*There are two BW questions! Answer: “A”

Answer: “C”

Answer: “B”

Answer: “C”

Now some other flashback questions! Answer: “H”

Answer: “H”

Answer: “F”

Answer “H”

Answer: “D”

Answer: “G”

Wave Behavior Reflection occurs when a wave strikes an object or surface and bounces off. Your echo is reflected sound waves bouncing off walls, floors, ceilings, people and objects. You can see your refection in a mirror when light waves bounce off your face, strike the mirror, and reflect back to your eyes.

Wave Behavior The bending of a wave as it moves from one medium into another is called refraction. The speed of a wave can be different in different materials. For example, light waves travel faster in air than in water. Refraction occurs when the speed of a wave changes as it passes from one substance to another.

Refraction

Refraction

Wave Behavior Diffraction is the bending of waves around a barrier. This is why you can hear music coming out of the band room even though you are all the way down the hallway. The sound waves bend as they pass through the open doorway.

Wave Behavior What happens when waves meet? Waves pass right through each other and continue moving. During the time the two waves overlap, they combine and form a new wave. This is called interference. Once they are no longer overlapping, they continue to move with the same wavelength and amplitude they had before.

Interference Constructive interference is when the crest of one wave overlaps the crest of another. This makes the amplitude larger. Destructive interference occurs when the crest of one wave overlaps the trough of another. This makes the amplitude smaller.