4.1 Wave Properties PDF

4.1 UNIT 4 WAVE PROPERTIES Waves & Electromagnetic Radiation INTRO: “HOW DO WAVES TRAVEL?” 1) Fill a shallow pan with about 3 cm of water. 2) With a pencil, touch the surface of the water on the left side of the pan twice, each second for 1 minute. 3) Describ...

4.1 UNIT 4 WAVE PROPERTIES Waves & Electromagnetic Radiation INTRO: “HOW DO WAVES TRAVEL?” 1) Fill a shallow pan with about 3 cm of water. 2) With a pencil, touch the surface of the water on the left side of the pan twice, each second for 1 minute. 3) Describe the pattern the waves make. a) Sketch a rough diagram of what you see. The object rocked 4) Float an object in the center of the pan. backand forth 5) Repeat Step 2 & observe how the object moves. a) Sketch a rough diagram of what you see. ENERGY & WAVES ➔ wave = any disturbance that transfers ENERGY from place to place ◆ medium = material/matter a wave travels through ◆ vacuum = completely empty space ➔ mechanical wave = Ia wave that REQUIRES a medium through which to travel ◆ example: sound waves ENERGY & WAVES ◆ Sound waves are produced when a source of energy causes a medium to vibrate. a repeated back-&-forth or up-&-down motion ➔ electromagnetic radiation = a wave that does NOT REQUIRE a medium to travel ◆ examples: visible light, radio waves, x-rays, microwaves E medium  electromagnetic 0 mechanical TYPES OF WAVES ➔ Mechanical waves are classified by the direction of how they move. ◆ 2 main types: transverse & longitudinal ➔ transverse wave ◆ travels perpendicular (right angle, 90°) to the direction of the source’s motion example: you move a rope up & down ◆ crest = high part of a transverse wave ◆ trough = low part of a transverse wave TYPES OF WAVES ➔ longitudinal wave ◆ travels parallel (in the same direction) to the vibrations ◆ compression = parts where the coils are close together ◆ rarefaction = parts where the coils are spread out, rarified TYPES OF WAVES ➔ surface wave ◆ combination of transverse & longitudinal waves ◆ moves in 2 directions (circular motion) ◆ example: ocean waves PROPERTIES OF WAVES ➔ Waves can carry a little OR a lot of energy, are short OR long, rare OR frequent, and are fast OR slow. ◆ basic properties: amplitude, wavelength, frequency, speed ➔ amplitude = distance between the HIGHEST crest & the resting position ◆ the more energy a wave has, the greater its amplitude PROPERTIES OF WAVES ➔ wavelength = distance a wave travels before it starts to repeat ◆ distance between 2 parts of a wave (crest to crest, trough to trough) ➔ frequency = amount of times a waves repeats ◆ number of complete waves that pass a given point in a certain amount of time ◆ measured in hertz (Hz) ◆ 1 wave per second = 1 Hz EXAMPLE: TRANSVERSE WAVE RESTING CREST WAVELENGTH POSITION AMPLITUDE TROUGH PROPERTIES OF WAVES ➔ speed = distance a wave travels in a certain amount of time ◆ different waves, different speeds Light travels almost 1 M times faster than sound (through air). ◆ different speeds through different materials Light travels faster through water than through glass. Sound travels faster through water than through air. PROPERTIES OF WAVES ◆ speed = distance / time ◆ wave speed = wavelength frequency ➔ Example: If you & a friend are standing at the opposite ends of the gym and one of you claps, will the other person hear the clap at the same time he or she sees it happen? Explain. WAVE ENERGY ➔ Waves transmit energy from place to place. ◆ depends on how much energy was INPUT by the original source of vibration FASTER vibrations transmit MORE energy LARGER amplitude vibrations transmit MORE energy ◆ A wave’s ENERGY is proportional to its frequency. ◆ A wave’s ENERGY is proportional to the SQUARE of its amplitude. WAVE ENERGY ➔ Example: Find the missing value from each wave. ➔ Example: What would happen to the ENERGY of the 10 am wave if the FREQUENCY increased to 6 Hz? WAVE ENERGY ➔ Example: If the AMPLITUDE of the 6 pm wave increase to 0.6 m, how many times greater would the ENERGY become? 4.1 LESSON CHECK 1) If the amplitude of ocean waves increases by a factor of 1.1, by how much does the energy increase? 2) A worker uses a jackhammer to break up a sidewalk. What kind of waves does the jackhammer produce? 4.1 LESSON CHECK 3) What does it mean to say that a wave is cyclic and periodic? 4) How do you measure the amplitude of a longitudinal wave? 4.1 LESSON CHECK Honors 5) A musician increases the wavelength of the sound waves she produces WITHOUT changing their speed. What must be happening to the frequency of the waves? Explain.