drop (liquid)

A drop is a small volume of liquid, bounded completely or almost completely by free surfaces. The simplest way to form a drop is to allow liquid to flow slowly from the lower end of a vertical tube of small diameter. When the pendant drop exceeds a certain size it is no longer stable and detaches itself. Drops may also be formed by the condensation of a supercooled vapor or by atomization of a larger mass of liquid. The weight of the largest drop that can hang from the end of a tube of radius a is nearly

mg=2πaλ cos α

where λ is the surface tension of the liquid and α is the angle of contact with the tube. This relationship is the basis of a convenient method of measuring surface tension. Due to the different refractive index of water and air, refraction and reflection occur on the surfaces of raindrops, leading to rainbow formation.

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digital transmission group
digitizer
digroup
direct access
direct connect
direct distance dialing
directional coupler
directive gain
direct sequence spread spectrum
disengagement originator
dispersion limited operation

distortion
distortion limited operation
distributed database
distributed queue dual bus
distributed switching
disturbance voltage
diurnal phase shift
diversity reception
dod master clock
double ended synchronization
double sideband reduced carrier transmission

double sideband suppressed carrier transmission
doubly clad fiber
d region
drift
drop and insert
dropout
dual access
dual in line package
duct
duobinary signal
duplexer

duty cycle
dynamic range
earth terminal complex
echo (mythology)
effective data transfer rate
effective earth radius
effective height
effective input noise temperature
effective mode volume
effective power
effective transmission rate