Waves, Sound and Optics Flashcards

1
Q

Hooke’s law

A

F = -kx

large k = stiff, strong spring

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2
Q

elastic potential energy

A

PE(elastic) = 1/2kx^2

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3
Q

elastic kinetic energy

A

KE(elastic) = 1/2mv^2

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4
Q

period and frequency relationship

A

f=1/T T=1/f

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5
Q

frequency of a spring

A

f = 1/2π√k/m

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6
Q

period of a spring

A

T = 2π√m/k

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7
Q

restoring force for a pendulum

A

F(restoring) = mgsinθ

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8
Q

frequency for a pendulum

A

f = 1/2π√g/l

l is length of pendulum, g gravity

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9
Q

period for a pendulum

A

T = 2π√l/g

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10
Q

KE and PE for a pendulum

A
KE = 1/2mv^2
PE = mgh
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11
Q

wave equation

A

v = fλ

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12
Q

2 big wave rules

A

1) same medium, same speed.
2) different medium, same frequency.
* these rules hold for transverse AND longitudinal waves!

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13
Q

standing wavelengths for 2 fixed ends, and fundamental wavelengths

A
λn = 2L/n, λn = λ1/n
n = nodes - 1
L = length of rope
λ1 = fundamental wavelength
*for first (fundamental) harmonic, n =1
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14
Q

standing wave frequencies for 2 fixed ends, and fundamental frequencies

A
fn = nv/2L, fn = n(f1)
n = nodes - 1
L = length of rope
f1 = fundamental frequency
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15
Q

describe the speed of sounds through different media

A

v = solids > liquids > gasses

faster with increased resistance to compression and decreased density

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16
Q

standing waves in a tube (both ends open)

A
λn = 2L/n
fn = nv/2L
17
Q

standing waves in a tube (one end open)

A

λn = 4L/n
fn = nv/4L
Only odd n!

18
Q

beat frequency

A

f(beat) = |f1 - f2|

19
Q

Intensity formula

A

β = 10log(10)I/Io
measures sound intensity in dB (intensity also measured in W/m^2)
add 10 to β, multiply I by 10
subtract 10 from β, divide I by 10

20
Q

the doppler effect

A

fo = fs ( v ± vo / v ± vs )

21
Q

speed of light in a vacuum

A

c = 3 x 10^8 m/s

22
Q

energy of a photon

A
E = hf = hc/λ
h = planck's constant
23
Q

energy is proportional to ____ for waves and ____ for particles.

A

square of amplitude

frequency

24
Q

index of refraction. I.O.R. for air? speed?

A

index of refraction = speed of light in vacuum/speed of light in medium
n = c/v
use n=1 for air
The greater n, slower speed.

25
Snell's law and implications
n1sinθ1 = n2sinθ2 - when second medium has higher n, moves slower and bends towards the normal - when second medium has lower n, moves faster and bends away from the normal
26
critical angle for total internal reflection
sinθcrit = n2/n1 If the angle of incidence is greater than θcrit, total internal reflection occurs Only occurs when going from high n1 to lower n2.
27
Focal length
``` f = 1/2Rc Rc = radius of curvature ```
28
Mirror/Lens equation
1/f = 1/o + 1/i o is always positive, i and f vary (+ if on same side as observer for mirror, + if on opposite side for lens) (if i is - virtual, if + real for both lenses and mirrors)
29
magnification equation
m = -i/o same for lenses and mirrors if m is + upright, - inverted
30
Lens power (also for multiple lenses)
P = 1/f (f must be in meters) | -'ve and +'ve f still applies
31
myopia and how to correct it
Myopia = nearsightedness, can't see far, image focused before the retina fixed with diverging lens
32
hyperopia and how to correct
hyperopia = farsightedness, can't see near, image focused beyond the retina fixed with converging lens
33
presbyopia and how to correct
presbyopia = inability to accommodate eye, corrected with converging lens.