What are coherent sources? Is it possible to observe interference patt

1.	What are coherent sources? Is it possible to observe interference pattern with light from any two different sources ? Why ?
Answer» Coherent sources : Two sources of light are said to be coherent if the phase difference between the emitted waves remains constant. It is not possible to observe interference pattern with light from any two different sources. This is because, no observable interference phenomenon occurs by superposing light from two different sources. This happens due to the fact that different sources emit waves of different frequencies. Even if the two sources emit light of the same frequency, the phase difference between the wave trains from them fluctuates randomly and rapidly, i.e., they are not coherent. Consequently, the interference pattern will change randomly and rapidly, and steady interference pattern would not be observed.

What are coherent sources? Is it possible to observe interference pattern with light from any two different sources ? Why ?

Answer»

Coherent sources : Two sources of light are said to be coherent if the phase difference between the emitted waves remains constant. It is not possible to observe interference pattern with light from any two different sources. This is because, no observable interference phenomenon occurs by superposing light from two different sources. This happens due to the fact that different sources emit waves of different frequencies. Even if the two sources emit light of the same frequency, the phase difference between the wave trains from them fluctuates randomly and rapidly, i.e., they are not coherent.

Consequently, the interference pattern will change randomly and rapidly, and steady interference pattern would not be observed.

Discussion

No Comment Found

Related InterviewSolutions

A pair of slits 1.5 mm apart is illuminated with monochromatic light of wavelength 5500 Å and the interference pattern is obtained on a screen 1.5 m from the slits. The least distance of a point from the central maximum where the intensity is minimum is (A) 0.275 mm (B) 0.55 mm (C) 2.75 mm (D) 5.5 mm.
In two separate setups of Young’s double-slit experiment, the wavelengths of the lights used are in the ratio 1 : 2 while the separation between the slits are in the ratio 2 : 1. If the fringe widths are equal, the ratio of the distances between the slit and the screen is (A) 1 : 4 (B) 1 : 2 (C) 2 : 1 (D) 4 : 1.
In Young’s double-slit experiment, the slit separation is reduced to half while the distance of the screen from the slits is increased by 50%. In terms of the initial fringe width, W, the new fringe width is,(A) \(\cfrac14\)W (B) \(\cfrac34\)W (C) \(\cfrac32\)W(D) 3 W
Using a monochromatic light of wavelength 2 in Young’s double-slit experiment, the eleventh dark fringe is obtained on the screen for a phase difference of(A) \(\cfrac{11}2\) π rad (B) \(\cfrac{21}2\) π rad (C) 13 π rad (D) 21 π rad
What is diffraction of light ? Give an example.
Two source S1 and S2 of intensity I1 and I2 are placed in front of a screen [Fig. 10.3 (a)]. The patteren of intensity distribution seen in the central portion is given by Fig. 10.3 (b). In this case which of the following statements are true. (a) S1 and S2 have the same intensities. (b) S1 and S2 have a constant phase difference. (c) S1 and S2 have the same phase. (d) S1 and S2 have the same wavelength.
The resolving power of a telescope of aperture 100 cm, for light of wavelength 5.5 × 10-7 m, is (A) 0.149 × 107 (B) 1.49 × 107(C) 14.9 × 107(D) 149 × 107
Unpolarised light is incident on a plane glass surface. What should be the angle of incidence so that the reflected and refracted rays are perpendicular to each other? (For glass refractive index = 1.5).
Unpolarized light is passed through two polarizers. Under what condition is the intensity of the emergent light (i) maximum (ii) zero?
Polarization of light CANNOT be produced by (A) reflection (B) double refraction (C) dichroism(D) diffraction.