Advertisements
Advertisements
Question
Obtain the equation for resolving the power of the microscope.
Advertisements
Solution
- A microscope is used to see the details of the object under observation. The ability of a microscope depends not only in magnifying the object but also in resolving two points on the object separated by a small distance dmin. Smaller the value of dmin better will be the resolving power of the microscope.
Resolving power of microscope
`"r"_0 = (1.22 lambda "v")/"a"` - then the magnification m is,
m = `"r"_0/"d"_"min"`
`"d"_"min" = "r"_0/"m" = (1.22 lambda"v")/"am" = (1.22 lambda "v")/("a"("v"//"u")) = (1.22 lambda"u")/"a"`
[∴ m = v/u]
`"d"_"min" = (1.22 lambda "f")/"a"` [∴ u ≈f]
On the other side,
2 tan β ≈ 2 sin β = `"a"/"f"` ∴ [a = f 2sin β]
`"d"_"min" = (1.22 lambda)/(2 sin beta)` - To further reduce the value of dmin the optical path of the light is increased by immersing the objective of the microscope into a bath containing oil of refractive index n.
`"d"_"min" = (1.22 lambda)/(2"n" sin beta)` - Such an objective is called oil-immersed objective. The term n sin β is called numerical aperture NA.
`"d"_"min" = (1.22 lambda)/(2 ("NA"))`
APPEARS IN
RELATED QUESTIONS
Answer the following question in detail.
Define and describe the magnifying power of an optical instrument.
Answer the following question in detail.
How does magnifying power differ from linear or lateral magnification?
Answer the following question in detail.
What is the limitation in increasing the magnifying powers of a simple microscope?
Why is oil-immersed objective preferred in a microscope?
What is myopia?
What is presbyopia?
What is astigmatism? What is its remedy?
Discuss about simple microscope and obtain the equations for magnification for near point focusing and normal focusing.
Discuss about astronomical telescope.
Mention different parts of the spectrometer.
The near point and the far point for a person are 50 cm and 500 cm, respectively. Calculate the power of the lens the person should wear to read a book held in hand at 25 cm. What maximum distance is clearly visible for the person with this lens on the eye?
A light wave of wavelength λ is incident on a slit of width d. The resulting diffraction pattern is observed on a screen at a distance D. If linear width of the principal maxima is equal to the width of the slit, then the distance D is
If astronomical telescope of length 1.53 m has magnifying power of magnitude 50, the values of fo and fe are ____________.
The magnifying power of a telescope is nine. When it is adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The focal length of objective and eyepiece are respectively.
The magnifying power of a telescope is high if its objective and eyepiece have respectively ______.
A simple microscope is used to see the object first in blue light and then in red light. Due to the change from blue to red light, what is the effect on its magnifying power?
Magnification produced by astronomical telescope for normal adjustment is 10 and length of telescope is 1.1 m. The magnification when the image is formed at least distance of distinct vision (D = 25 cm) is ______.
In the adjoining figure, AB represents the incident ray, and BK is the reflected ray. If angle BCF = θ, then ∠BFP is given by ______.
A camera objective has an aperture diameter of d. If the aperture is reduced to diameter d/2, the exposure time under identical conditions of light should be made ______.
