I'm pretty sure its for breathing!!
a gill cover is used to cover the gill on the fish
This is called the operculum
It is used to cover the gill on the fish.
A loophole is another term used to refer to an arrow slit in a defensive structure or fortification.
The formula used to calculate the separation of slits in diffraction experiments is: d / sin() where: d is the slit separation is the wavelength of the light used is the angle of diffraction
The width of the slit should be on the order of the wavelength of the light being used for diffraction in order to observe the diffraction pattern clearly. This is known as the single-slit diffraction condition. The size of the slit also affects the angular spread of the diffraction pattern.
Gill
The past tense and past participle forms are both 'slit'.
Slitting is the present participle of slit.
Pharyngeal slits are not gill slits. They are filter-feeding organs in non-vertebrates, and are used to strain matter and food from water.
Gill Sans.
slit, prism, and film plate