Physics Waves

SW - Strings

Created

Created by plucking, strumming, or rubbing a string.

SW - Strings

Length

Shorter strings have higher freq's due to a decreased wavelength. V=freq (increse) x wavelength (decrease)

SW - Strings

Tension

Tighter strings have higher freq due to increased speed. Wavelength and length are constant.

SW - Strings

Density

Lower density strings have higher freq's due to an increased speed.

SW - Strings

Temperature

Increase in temp causes strings to expand, reducing tension. Wavelength is constant (as ends of strings are fixed) so lower wave speed, thus lower freq of produced note.

SW - Strings

Pressing on strings

A node is formed, decreasing wavelength and increase freq. Length decreases. A different harmonic is created.

SW - Strings

For different notes/freq's to be played instruments must have either

- Strings of the same length, but different tensions and densities

or

- Strings of different lengths.

SW - Strings & Open Pipes

Equations

L=(#(WL)/2)

SW - All

Created

- Wave travels along & is reflected at the end

- Reflected wave interferes with og wave to produce a SW

- Wave must be at the fundamental frequency for pipe/string

- Waves meet in phase=constructive=antinode

- Waves meet out of phase=destructive=node

SW - Open Pipes

Blowing in different spots

Wavelength changes depending on where you blow.

SW - Open & Closed Pipes

Longer pipe

Larger wavelength, freq decreases. Speed of sound is unchanged.

SW - Closed Pipes

Temp

Increase in temp causes speed of sound in air to increase. Wavelength is fixed (as length doesn't change), hence a higher freg note is produced.

SW - Closed Pipes

Different harmonics

Blowing harder or opening or closing air holes along the pipe, creating an antinode, decreasing wavelength and increasing freq of produced note as waves travel less distance.

SW - Closed

Equations

L=(#(WL)/4)

Sharper Pattern

More slits create more wave sources that can interfere

Brighter Pattern

- More light can pass through with greater number of slits

- Constructive occurs (in phase waves)

- Path difference is a whole number of WL's

Dark regions

- Destructive occurs (out of phase waves)

- Path difference = (N-0.5)WL

Narrower Slits

Dark regions are wider

Slits are Closer Together

Fringes move further apart N(WL)=dsin˚,d decreases=sin˚ & ˚ increase=pattern covers more area. N(WL)/pathdifference & WL are unchanged. Less maxima, sharper & brighter pattern. More sources of interference.

Out of Phase Slits

Destructive interference occurs, so area with no light occurs

Brighter in the middle

Most constructive occurs as there is the most overlapping of waves

Red light

Longest wavelength, angle, path difference & greatest diffraction. Largest angle = forms maxima at largest angle, hence red light is formed on the outside of each spectrum.

Violet light

Smallest wavelength, angle, path difference & smallest diffraction. Smallest angle = forms maxima at smallest angle, hence violet light is formed on the inside of each spectrum.

Thickness of string

• Speed changes

• WL is unchanged

• F=(V/WL)= freq changed

Dopler - Source traveling betweeen two objects

• Towards and object: waves bunch up infront of sources, hence WL decrease.

• Speed is constant.

• F=V/WL so freq increases.

• Visa versa for source traveling away from object.

Beats

• Two waves interfere to become a new wave

• Beat freq is what is heard

• (f1-f2=beat freq)

• Loud spots occur when waves meet in phase and constructive interference occurs.

• Quiet spots occur when waves meet out of phase & destructive interference occurs.