Download App

Wave Optics — Physics STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsWave Optics4 Marks
Question
What are the conditions for obtaining good interference pattern? Give reasons.
✓

Answer

The conditions necessary for obtaining well defined and steady interference pattern :
  1. The two sources of light should be coherent:
    The two sources must maintain their phase relation during the time required for observation. If the phases and phase difference vary with time, the positions of maxima and minima will also change with time and consequently the interference pattern will change randomly and rapidly, and steady interference pattern would not be observed. For coherence, the two secondary sources must be derived from a single original source.
  2. The light should be monochromatic :
    Otherwise, interference will result in complex coloured bands (fringes) because the separation of successive bright bands (fringes) is different for different colours. It also may produce overlapping bands.
  3. The two light sources should be of equal brightness, i.e., the waves must have the same amplitude.
    The interfering light waves should have the same amplitude. Then, the points where the waves meet in opposite phase will be completely dark (zero intensity). This will increase the contrast of the interference pattern and make it more distinct.
  4. The two light sources should be narrow :
    If the source apertures are wide in comparison with the light wavelength, each source will be equivalent to multiple narrow sources and the superimposed pattern will consist of bright and less bright fringes. That is, the interference pattern will not be well defined.
  5. The interfering light waves should be in the same state of polarization :
    Otherwise, the points where the waves meet in opposite phase will not be completely dark and the interference pattern will not be distinct.
  6. The two light sources should be closely spaced and the distance between the screen and the sources should be large : Both these conditions are desirable for appreciable fringe separation. The separation of successive bright or dark fringes is inversely proportional to the closeness of the slits and directly proportional to the screen distance.

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 "Answer the following in Detail" from Wave Optics→Wave Optics — all question types→Physics STD 12 Science question papers→Maharashtra Board STD 12 Science question papers→Maharashtra Board question paper generator→

Similar questions

Two cells of emf $1.5$ Volt and $2$ Volt having respective internal resistances of $1 \Omega$ and $2 \Omega $ are connected in parallel so as to send current in same direction through an external resistance of $5 \Omega $. Find the current through the external resistance.
→
Derive an expression for the impedance of an $LCR$ circuit connected to an $AC$ power supply.
→
Find the heat needed to melt 100 grams of ice at $0^{\circ} C$, at a pressure of $1.013 \times 10^5 N / m ^2$. What is the work done in this process? What is the change in the internal energy of the system ?
Given : Specific latent heat of fusion of ice $=79.71 cal / g$, density of ice $=0.92 g / cm ^3$, density of water $=1 g / cm ^3, 1 cal =4.186 J$.
→
Describe the construction and working of a transformer with a neat labelled diagram.
→
State and explain Rayleigh's criterion for minimum resolution.
→
A wave of frequency $500\ Hz$ is travelling with a speed of $350\ m/s.$
(a) What is the phase difference between two displacements at a certain point at times $1.0$ ms apart?
(b) what will be the smallest distance between two points which are $45^\circ$ out of phase at an instant of time?
 
→
A $15.0 \mu F$ capacitor is connected to a $220\ V, 50\ Hz$ source. Find the capacitive reactance and the current (rms and peak)
in the circuit. If the frequency is doubled, what will happen to the capacitive reactance and the current.
→
Explain the concept of self induction.
→
A stretched sonometer wire emits a fundamental note of frequency $256 Hz$. Keeping the stretching force constant and reducing the length of the wire by $10 cm$, the frequency becomes $320 Hz$. Calculate the original length of the wire.
→
A big dumb-bell is prepared by using a uniform rod of mass $60\ g$ and length $20\ cm.$ Two identical solid thermocol spheres of mass $25\ g$ and radius $10\ cm$ each are at the two ends of the rod. Calculate moment of inertia of the dumbbell when rotated about an axis passing through its centre and perpendicular to the length.
 
→