What is meant by the resolving power of an optical instrument? Drawing suitable diagrams explain Rayhigh's Criterion for the limit of resolution of two very close spectral lines. Write formula for the resolving power of (i) Microscope (ii) Telescope.
Give explaination in 40-60 words.
Answers
Answer:
Light diffracts as it moves through space, bending around obstacles, interfering constructively and destructively. While this can be used as a spectroscopic tool—a diffraction grating disperses light according to wavelength, for example, and is used to produce spectra—diffraction also limits the detail we can obtain in images. Figure 1a shows the effect of passing light through a small circular aperture. Instead of a bright spot with sharp edges, a spot with a fuzzy edge surrounded by circles of light is obtained. This pattern is caused by diffraction similar to that produced by a single slit. Light from different parts of the circular aperture interferes constructively and destructively. The effect is most noticeable when the aperture is small, but the effect is there for large apertures, too.
Answer:
Resolving Power of Optical Instruments
Explanation:
Limit of resolution of optical instruments
In determining the limit of resolution of optical instruments like a telescope or a microscope, for the two stars to be just resolved,
fΔθ≈r0≈ 0.61λf/a
implying Δθ≈ 0.61λ/a
Thus Δθ will be small if the diameter of the objective is large. This implies that the telescope will have better resolving power if a is large. It is for this reason that for better resolution, a telescope must have a large diameter objective.
DEFINITION
Resolving Power of Microscope
The resolving power of a microscope is defined as the reciprocal of the distance between two objects which can be resolved when seen through the microscope.
Resolving Power = 1/Δd = 2 μ sinβ/1.22λ
DEFINITION
Resolving Power of Optical Instruments
Resolving Power of Optical Instruments: A quantity that characterizes the ability of optical instruments to produce separate images of two points of an object that are close to each other. The smallest linear or angular distance between the two points at which their images begin to merge is called the linear or angular limit of resolution. The inverse quantity usually serves as a quantitative measure of the resolving power.
Because of the diffraction of light at the edges of optical components, even in an ideal optical system (that is, one without aberrations), the image of a point is not a point but a central disk of light surrounded by rings, which are alternately dark and light in monochromatic light and rainbow-colored in white light.
