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Questions
Explain the construction and working of a ‘Compound Microscope’.
With the help of a ray diagram, describe the construction and working of a compound microscope.
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Solution
Construction:
- A compound microscope consists of two convex lenses. The lens with the shorter focal length is placed near the object, and is called an ‘objective lens’ or ‘objective piece’.
- The lens with a larger focal length and larger aperture placed near the observer’s eye is called an ‘eye lens’ or ‘eyepiece’.
- Both lenses are fixed in a narrow tube with an adjustable provision.
Image formation in a compound microscope
Working:
- The object (AB) is placed at a distance slightly greater than the focal length of the objective lens (u > f0).
- A real, inverted, and magnified image (A’B’) is formed at the other side of the objective lens.
- This image behaves like the object for the eye lens. The position of the eye lens is adjusted in such a way that the image (A’B’) falls within the principal focus of the eyepiece.
- This eyepiece forms a virtual, enlarged, and erect image (A” B”) on the same side of the object.
- A compound microscope has 50 to 200 times more magnification power than a simple microscope.
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A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is ______.
What is a simple magnifier or microscope defined as?
What is the aim when using a simple microscope regarding the nature of the image formed?
If the object is placed at a distance slightly less than the focal length of a simple microscope lens, what is the nature and location of the closest comfortable viewing distance for the image?
What is the value of the near point distance \[D\] used for comfortable viewing?
Using the relation \[m = \frac{v}{u} = v\left(\frac{1}{v} - \frac{1}{f}\right)\] and the sign convention where \[v\] is negative and equal in magnitude to \[D\], what is the linear magnification \[m\] for the image formed at the near point by a simple microscope?
Since \[D\] is about 25 cm, what focal length of convex lens is needed to achieve a magnification of six with a simple microscope?
What is the angular magnification of a simple microscope when the image is formed at infinity?
How does the magnification when the image is at infinity compare with the magnification when the image is at the near point, and which viewing condition is more comfortable?
What is the maximum magnification of a simple microscope for realistic focal lengths, and what arrangement is used to achieve much larger magnifications?
In a compound microscope, what type of image does the objective form of the object, and what role does this image serve?
In a compound microscope with \[f_o = 1.0\ \text{cm}\], \[f_e = 2.0\ \text{cm}\], and tube length \[L = 20\ \text{cm}\], what is the total magnification when the image is formed at infinity?
