What categories of measurement techniques do you know?
contact- vs non-contact measurement methods
point vs area/volume measurement methods
direct- vs indirect measurement methods
Name non-optical measurement techniques for droplet dynamic application.
collection of drops (in cells, on slides)
force impactors
charged wire techniques
Explain the working principle of one non-optical technique.
Charged wire technique:
A wire changes its electrical properties depending on the amount of fluid that is interacting with the wire. The setup has to be calibrated.
…
How to measure surface tension?
Mechanical:
DeNoüy ring method
Ironing method by Lenard
Wilhelmy plate method
Capillary rise method
Droplet mass
Bubble pressure
Optical:
Pendant droplet method
Sessile droplet method
Sessile bubble method
Capillary / surface waves
Explain the method …. for measuring surface tension.
What is the basic principle of the Wilhelmy plate tensiometer?
What is the main difference between surface tension- and viscosity measurement methods?
For measurement of the viscosity, the fluid has to move.
How to measure viscosity?
U-tube viscometer (e.g. Ubbelohde type)
Falling sphere viscometers
Rotation viscometers
Vibration viscometers
Explain the method …. for measuring viscosity.
What is the basic principle of the Ubbelohde viscometer?
Hagen-Poiseuille law
(Flow rate through thin capillary)
What definitions of light do you know?
electromagnetic wave
particle like behaviour (photon)
What are the axioms of geometric optics?
in homogeneous isotropic material, the light rays are straight.
At the boundary between two homogeneous isotropic materials, light is generally reflected and refracted according to the laws of reflection and refraction.
The beam path is reversible, the direction of light on a light beam is irrelevant.
The light rays cross each other without influencing each other.
Why use a simplification like geometric optics at all?
What is the law of refraction?
What is the refractive index?
c: speed of light in vacuum
v: speed of light in according material
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