14.2 Waves cont. 14.2 Waves cont.

Getting crazier and crazier!Getting crazier and crazier!

Stayin’ up or flippin’ down?Stayin’ up or flippin’ down?

When a wave bounces When a wave bounces off a fixed end that off a fixed end that does not move, the does not move, the wave will invert.wave will invert.

If the wave reflects off a If the wave reflects off a free end, the wave free end, the wave will stay upright.will stay upright.

Superposition to the rescue!Superposition to the rescue!

Waves don’t just do their own thing, they are Waves don’t just do their own thing, they are constantly interfering with one another. constantly interfering with one another. This is known as This is known as interferenceinterference and can be and can be either either constructiveconstructive, when the displacement , when the displacement is in the same direction, or is in the same direction, or destructivedestructive when the displacement is in opposite when the displacement is in opposite directions. directions.

Ode to the nodeOde to the node

When to waves sync up and created a standing wave, there are positions of maximum and minimum displacement.

A point of zero displacement is called a node and a point of maximum displacement is known as an antinode.

http://www.physics.ohio-state.edu/~ntg/reu/pulses.html

I’m bouncin’ off the walls again…I’m bouncin’ off the walls again…

Waves are constantly bouncing off of surfaces. Waves are constantly bouncing off of surfaces.

The wave going to the surface is called the The wave going to the surface is called the incidentincident wave. wave.

The wave coming off the surface is the The wave coming off the surface is the reflectedreflected wave.wave.

Angle’s alikeAngle’s alike

The The Law of ReflectionLaw of Reflection states that the angle states that the angle of incident, of incident, θθii,, will equal the reflected will equal the reflected

angle, angle, θθrr..

incident reflected

normal

Θi Θr

Bending in the breezeBending in the breeze

The speed at which a wave travels depends on The speed at which a wave travels depends on the medium it travels in. As a wave passes the medium it travels in. As a wave passes between two boundaries, its wavelength between two boundaries, its wavelength changes which causes it to change direction. changes which causes it to change direction. This effect is known as This effect is known as refractionrefraction. .

To maintain the same frequency, the wave must change speed as it changes medium.

Diffraction Action!Diffraction Action!

As a wave passes the edge of a boundary it As a wave passes the edge of a boundary it bends around the edges. This bending is bends around the edges. This bending is known as known as diffractiondiffraction and can create some and can create some interesting effects. The fuzziness of interesting effects. The fuzziness of shadows is a direct cause of this effect. shadows is a direct cause of this effect. When two waves diffract near each other, When two waves diffract near each other, they interfere with one another.they interfere with one another.

Single or a double?Single or a double?

Single Slit Double Slit

Dark areas represent destructive interference, (wave amplitude decreases), and bright areas represent constructive interference (wave amplitude increases)

““It would be possible to describe everything scientifically, It would be possible to describe everything scientifically, but it would make no sense; it would be without but it would make no sense; it would be without meaning, as if your described a Beethoven meaning, as if your described a Beethoven

symphony as a variation of a wave pressure.”symphony as a variation of a wave pressure.”

- Albert Einstein

HW – Pg 345 # 20, 22, 23, 45, 47HW – Pg 345 # 20, 22, 23, 45, 47