medphysics equations

sound pressure P

P(t)= DP sinj

DP: max. pressure (- decrease, + increase)

t: time

j: phase of given mechanical wave

sound intensity

The sound intensity is the power per unit area carried by a sound wave, typically expressed in watts per square meter (W/m²). It is proportional to the square of the sound pressure.

sound wavelength

acoustic impedance

Z = p x v

p - density of medium

v - sound velocity

sound intensity E

▪ E is defined at 1000 Hz sound freq.)

▪ I = intensity of sound

• I0 = threshold at 1000 Hz

▪ E is measured by B or dB

loudness of sound

▪ k= coefficient depending on frequency

▪ I0 = threshold of audibility of sound

▪ L is measured in Phon

reflection coefficient

mass transfer

M= -D x dc/dx x S x t

• M = mass

• D = diffusion coefficient

• dc/dx = concentration gradient

Laplace law additional pressure

Dp = 2s/r

• s = coefficient of surface tension

• r = radius of curvature (tube, blood vessel)

steady flow formula

S . v = Q à constant

Reynolds number

electric current strength

AC current relation

V = V0 . sin(2Pf.t)

• V = voltage at time t

• V0 = peak voltage

• f = frequency in Hz

AC time relation

I = I0 . sin(2Pf.t)

• I = current at time t

• I0 = peak at current

electrical resistance

Ohm’s law

Doppler shift

Precession frequency

o Precession frequency: V0 = g . B0

▪ V0 = resonant frequency

▪ g = gyromagnetic number

▪ B0 = magnetic field intensity

Beer-Lamber-Bouguer law

light absorption

Y = Y0 ead

▪ a = molar absorptivity coefficient e and concentration c

▪ a = e.c

photoelectric absorption

internal friction

amount of heat transferred

braking roentgen radiation

E = e.U • e = electron’s charge • U = voltage applied between cathode and anode

Poiseuille’s law

electrical resistance

capacitance

capacitive reactance

inductivity and inductive reactance

J= π.Δp.r 4/ 8.η.L , quantities involved are

1 Poiseuille’s law,

2 J is amount of fluid flowing,

3 Δp is pressure gradient,

4 r 4 is the radius of the pipe raised in four degree

5 η is viscosity

6 L is the length of the pipe

reflection coefficient

transmission coefficient

magnification of optical microscope

haemodialysis

Doppler ultrasound imaging

audiogram