<span>When someone is performing a very routine phlebotomy, which is the act of inserting a needle in a vein to draw blood, the most commonly used needle are needles with gauges of 20 or 21.</span>
With a light microscope one can view the nucleus and endoplasmic reticulum, large vacuoles etc
The resolution of a light microscope is dependent on the wavelength of light that is the main beam of illumination. Light has approximately 0.4 um (UV)- 0.7um (Infrared) wavelength. Organelles smaller than about 0.5 um will be difficult to discern with a light microscope.
With an electron microscope one can view, in addition, even the ribosomes and mitochondria, chromosomes, tubules etc.
An electron microscope can discern very minute details of a cell. This is because its resolution is dependent on the very small wavelength of a beam of electrons which is approximately 0.002 um (about 10,000 times powerful than a light microscope)
The statement that is correct regarding the troposphere and the stratosphere is The ozone layer is in the stratosphere. The third one is true. The ozone layer acts as a protection layer that prevents UV light.
<h3>What are the layers of the atmosphere?</h3>
The atmosphere is divided into many layers, with the troposphere close to the earth and the thermosphere toward the sun, as shown in the diagram. in between two layers, such as the tropopause, which is present between the troposphere and the stratosphere. In the stratosphere, the ozone layer is present, which prevents the sun's UV rays from falling on the earth, and the troposphere is the region where the clouds are formed.
Hence, the correct answer is the third option, which is "The ozone layer is in the stratosphere."
Learn more about the atmosphere here.
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