Question

Introduction to microscopy:

1- Interection of colored threads question:

- Can you use the fine adjustment knob so that you can focus on all three threads simultaneously when viewing them under higher power? why or why not?

2- Cork cells question:

- Cork can float on water. As you examine cork under a microscope, what features do you observe that might account for this characteristic?

3- Dust slide question:

- What materials can you see in dust under a microscope?

4- Tick/Mite slide question:

- Describe how you can quantify the size difference between the tick and the mite using a microscope.

Answer 1

1.No.Fine adjustment knob cannot be used to focus all the three threads simultaneously when viewing them under high power.First we have adjust the view using coarse adjustment.High power objective cannot focus all the three threads at a time.It can focus on only one thread at a time.Depth of field is the distance at which the image is said to be in focus.Depth of focus decreases with higher magnification .So using fine adjustment knob under high power reduces the depth of focus and and a smaller part of the specimen will be in focus.Thus the three threads cannot be focused simultaneously.Filed of view is also high for low power objective.So to focus all the three threads simultaneously you have to use low power objective as it has highest depth of focus.

2.Cork is able to float in water because cork is less dense than water.Cork cells are dead cells on the epidermis of the plant.They are found in herbaceous plants and woody dicots.It is filled with tannin,suberin etc.The floating property depends upon the specific gravity of the cork.Specific gravity of cork is the density of cork to the density of water or any other substance.Cork floats in water because it is less dense than water.The features that account for its less density when looked under microscope are:

Under microscope ,cork cell appears like a honeycomb structure.These compartment filled with a waxy substance called suberin.Suberin is highly impermeable to water.And so many holes are visible in cork cells.These holes are filled with air and makes it less dense.Suberin is lined in the cell wall of the cork cells.As it prevents water and gases from entering into the cell the cavity or inner part of cell remains hollow and makes it less dense.

3.Depending upon the place from where dust is collected,you can see different things in dust.If collected from an open space ,it contains pollen,spores,small insects,moulds,microorganisms etc.If collected from places near cities,there will be soot,particles emitted from vehicles etc.From floor sweepings,there will be hairs of human and pet,skin cells,particles of food,textile Fibres and sometimes dust mites.

4.In terms of quantity,more number of mites is visible than mites under the same magnification.Both ticks are mites are members of same class Arachinidae.Ticks are visible to naked eye and large in size compared to mites.Ticks are 1 mm long and grow upto 3 mm when adult.But mites are less than a millimeter and not visible to naked eyes.So in terms of size,ticks appears bigger than mites in microscope under same magnification.