WAVES

Traveling disturbanceTransfer of energy 2) Mechanical Wave- need a medium 1) Electromagnetic Wave 1) transversetransverse 2) longitudinallongitudinal pulse Two Wave Categories: Two Types of Mechanical Wave Motions:

WAVES Periodic Waves (repeats a pattern, or cycle) wavelengthperiodfrequency amplitude (Related to the energy content of a mechanical wave)

A sound wave traveling through air has a frequency of 425 Hz and a wavelength of meter. What is the speed of this sound wave? WAVES

WAVE SPEED depends on material properties of the medium (constant in a given medium) In a rope (or similar material), the speed of a wave is determined by: Tension in rope Linear density of rope

A transverse periodic wave is created in a rope of mass 2.00 kg and length of 6.00 meters. The rope is under a tension of 150 N. The speed of the wave in the rope would be… The wave cycles created in the rope have a period of 0.10 second. The wavelength of the “rope” wave would be… WAVE SPEED

You are in your car sitting at a red light when you hear an ambulance siren. You can not see the ambulance, yet you know it is approaching you. How can you tell the ambulance is moving toward you?

The intensity DECREASES as the distance from the source increases.

The siren is producing sound energy at a rate of 3.6 W, and you are 10.7 meters away from the siren. What is the intensity of the sound at your location?

If your eardrum has an area of 0.50 cm 2, how much energy passes through your eardrum in a time of 5.0 seconds?

What would the intensity be at a distance of 1070 meters?

Wave Behaviors

Reflection Changing direction upon meeting a barrier (wave energy remains in original medium) The polarity (orientation) of the wave may also be affected: If the barrier is very rigid compared to the original medium, the reflected wave will be inverted (have the opposite polarity of incident wave). If the barrier is very flexible compared to the original medium, the reflected wave will be upright (have the same polarity as incident wave).

How much of the wave energy will reflect? If barrier material is very different from original medium, most of the wave energy will reflect. If barrier material is very similar to original medium, very little of the wave energy will reflect. (Most will transmit through to the new medium.) Reflection

Path of reflected wave is determined by the Law of Reflection. Reflection (measured relative to the normal line) (transmitted portion not shown)

Refraction changing direction when the wave enters a new medium Incident wave must make θ > 0˚ to normal line. Which way will it bend? Caused by the wave changing speed when it enters the new medium. If wave slows down, it bends toward the normal. If wave speeds up, it bends away from the normal. (Wave frequency remains the same.)

I have a BB machine gun, which emits a continuous stream of metal BB’s. I point it at a metal plate that has two openings in it and shoot. If the metal plate is placed a certain distance in front of a plaster wall, what will I see on the wall when I move the plate away?

What if it is a beam of light instead?

Diffraction bending around obstacles in its path, changing direction as a result Wave speed remains constant since medium doesn’t change. Wave frequency also remains constant. The extent of the diffraction depends upon the wavelength of the waves (λ) and the size of the obstacle (d). Generally:

Interference The effect on the medium when multiple waves meet at the same location. constructive interference Principle of Linear Superposition – the resulting disturbance is the sum of the individual wave disturbances destructive interference circular wave interference(2D)

WAVES Upon entering a new medium… …what changes? …what remains the same? speed, wavelength, amplitude, possibly direction FREQUENCY