# Microscope and its working – Science

This video Microscope and its working is a science lesson/ tutorial for Grade 8-10 students.

Microscope

Microscope is an optical device which makes image of small object to appear very large.
The image is said to be magnified when the size of the image is larger than the size of the object.
The image is said to be magnified when the ratio size of the image is larger than the size of the object.
The ratio of the size of the image represented as v to the size of the object represented as u is called magnification factor.
i.e.
v/u = M
Similarly, if the size of the image is smaller than the size of the object, then the image is said to be diminished.
For v/u = M, if M is greater than 1, then image is magnified.
And if M is lesser than 1, then image is diminished.

Look at the word Physics on a white sheet of paper.
Now, take a convex lens and adjust the distance between the word on the board and the lens suitably so that the letters of the words physics appear big.
Hence, a convex lens is also called a simple microscope.
Let us understand the principle and working of a compound microscope.
To obtain a greater magnification, an optical device called compound microscope is used.
A compound microscope is a combination of two convex lens whose focal lengths are different.
The lens with the short focal length (f) will be facing the object.
This lens is called objective.
The lens with large focal length (F) is used for viewing the object.
This lens is called eye piece.
The two lens are so arranged that their optic centres lie on the same line.
The objective in the eye piece are fitted to one end of two separate tubes.
The two tubes are such that one tube fits into the other and slides freely.

Seeing an inverted image is not a disadvantage as the microscope is used to observe very small objects such as bacteria, blood cells, to measure the diameter of a capillary or cross section of a thin wire.