Download App

Wave Optics — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsWave Optics3 Marks
Question
Define resolving power of a microscope. Write its formula. How will it be affected when
(i) the wavelength of incident light decreases and
(ii) the aperture of the objective decreases ?
✓

Answer

Resolving power of Microscope : The resolving power of a microscope is its ability to show two nearby closely lying objects as just distinguished and it is equal to the reciprocal of its limit of resolution.
Image
"The resolving power of a microscope is defined as the reciprocal of the minimum distance between two point-objects which are seen distinctly separated through the microscope." According to Abbe, this minimum distance is given by :
$s=\frac{1.22 \lambda}{2 n \sin \alpha}$, ... (1)
where $ \lambda $ is the wavelength of the light, $n$ is the refractive index of the transparent medium between the objects and the objective of the microscope and $ \alpha $ is half the angle of the cone of light from any one object. Thus
Resolving Power :
$ R.P.=\frac{2n \sin \alpha}{1.22\lambda} $ ... (2)
From above formula (2) it is obvious that :
(i) when $ \lambda $ decreases, resolving power will be increased.
(ii) when aperture of objective is decreased the value of $ \alpha $ will be decreased. Hence R.P. will be decreased.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "3 Marks Question" from Wave Optics→Wave Optics — all question types→Physics STD 12 Science question papers→Rajasthan Board STD 12 Science question papers→Rajasthan Board question paper generator→

Similar questions

The figure below shows planer loops of different shapes moving out of or into a region of the magnetic field which is directed normal to the plane of the loops away from the reader. Determine the direction of induced current in each loop using Lenz's law. Check if you would obtain the same answers by considering the magnetic force on the charge inside the moving loops.

Image
→
Use Bohr’s postulates hydrogen atom to deduce the expression for the kinetic energy $(K.E.)$ of the electron revolving in the $n^{th}$ orbit and show that, $K.E. \frac{\text{e}^{2}}{8\pi\varepsilon_{0}\text{ e}_{n}} , $ where $r_n$ is the radius of the $n^{th}$ orbit. How is the orbit. How is the potential energy in the orbit related to the orbital radius orbit related to the orbital radius $r_n?$
→
A resistance $\text{R}=4\Omega$ is connected to one of the gaps in a meter bridge, which uses a wire of length 1m. An unknown resistance $\text{x}>4\Omega$ is connected in the other gap as shown in the figure. The balance point is noticed at ‘l’ cm from the positive end of the battery. On interchanging R and X, it is found that the balance point further shifts by 20cm (away from the end A). Neglecting the end correction calculate the value of unknown resistance ‘X’ used.
→
Draw the typical input and output characteristics of an $\text{n - p - n}$ transistor in $CE$ configuration. Show how these characteristics can be used to determine
$(a)$ the input resistance $(r_i),$ and
$(b)$ current amplification factor $(\beta).$
→
Using $\text{B}=\mu_0\text{H},$ find the ratio $\frac{\text{E}_0}{\text{H}_0}$ for a plane electromagnetic wave propagating through vacuum. Show that it has the dimensions of electric resistance. This ratio is a universal constant called the impedance of free space.
→
When an object cools down, heat is withdrawn from it. Does the entropy of the object decrease in this process? If yes, is it a violation of the second law of thermodynamics stated in terms of increase in entropy?
→
The work function for a certain metal is $4.2 eV.$ Will this metal give photoelectric emission for incident radiation of wavelength $330\ nm?$
→
  1. Describe briefly three experimentally observed features in the phenomenon of photoelectric effect. 
  2. Discuss briefly how wave theory of light cannot explain these features.
→
In a Coolidge tube, electrons strike the target and stop inside it. Does the target get more and more negatively charged as time passes?
→
  1. Draw a ray diagram depicting the formation of the image by an astronomical telescope in normal adjustment.
  2. You are given the following three lenses. Which two lenses will you use as an eyepiece and as an objective to construct an astronomical telescope? Give reason.
Lenses Power $(D)$ Aperture $(cm)$
$L_1$ $3$ $8$
$L_2$ $6$ $1$
$L_3$ $10$ $1$
→