Advertisements
Advertisements
Question
What kind of fringes do you expect to observe if white light is used instead of monochromatic light?
Advertisements
Solution
White light consists of waves of all wavelengths starting from violet to red colour. If the monochromatic light in Young’s interference experiment is replaced by white light, then the waves of each wavelength form their separate interference patterns. The resultant effect of all these patterns is obtained on the screen.
The path difference between waves starting from S1 and S2 at the location (M) of central fringe is zero, i.e., for point M of screen S1M − S2M=0 i.e., the waves of all colours reach at midpoint M in the same phase. Therefore the central fringe (at M) is white. As fringe width ω = Dλ/d or ω ∝ α and in visible region wavelength of violet colour is least and that of red colour is maximum, i.e., wavelength increases in the order of colours denoted by VIBGYOR therefore on either side of it some coloured fringes are obtained in order of colour VIBGYOR. That is the violet (V) fringe appears first and the red (R) the last. After this, the fringes of many colours overlap at each point of the screen and so the screen appears uniformly illuminated.
Thus if we use white light in place of monochromatic light the central fringe is white, containing on either side a few coloured fringes (in order VIBGYOR) and the remaining screen appears uniformly illuminated.
APPEARS IN
RELATED QUESTIONS
Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays '1' and '2' are respectively 1.3 and 1.5. Trace the path of these rays after entering the prism.
Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays '1' and '2' are respectively 1.35 and 1.45. Trace the path of these rays after entering the prism.
When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a reduction in the energy carried by the wave?
In the wave picture of light, the intensity of light is determined by the square of the amplitude of the wave. What determines the intensity in the photon picture of light?
State the essential conditions for diffraction of light ?
State Huygen’s principle. Using this principle explain how a diffraction pattern is obtained on a screen due to a narrow slit on which a narrow beam coming from a `=> n = (vlamda)/(vlamda_omega)`monochromatic source of light is incident normally.
Can the interference pattern be produced by two independent monochromatic sources of light? Explain.
Monochromatic fight of wavelength 198 nm is incident on the surface of a metallic cathode whose work function is 2.5 eV How much potential difference must be applied between the cathode and the anode of a photocell to just stop the photocurrent from flowing?
(a) Can the interference pattern be produced by two independent monochromatic sources of light? Explain.
(b) The intensity at the central maximum (O) in Young's double-slit experimental set-up shown in the figure is IO. If the distance OP equals one-third of the fringe width of the pattern, show that the intensity at point P, would `"I"_°/4`
(c) In Young's double-slit experiment, the slits are separated by 0⋅5 mm and the screen is placed 1⋅0 m away from the slit. It is found that the 5th bright fringe is at a distance of 4⋅13 mm from the 2nd dark fringe. Find the wavelength of light used.
A monochromatic ray of light falls on a regular prism under minimum deviation condition. What is the relation between angle of incidence and angle of emergence?
