Q. 32

# The line-width of a bright fringe is sometimes defined as the separation between the points on the two sides of the central line where the intensity falls to half the maximum. Find the line-width of a bright fringe in a Young’s double slit experiment in terms of λ. d and D where the symbols have their usual meanings.

Answer :

Given, separation between the slits

The distance between the screen and the slit,

Wavelength of light, .

Let the maximum intensity be and the intensity at y be .

Given,

therefore, path difference,

But the fringe extends to both sides of the maximum. Hence, the line width is

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A glass surface is coated by an oil film of uniform thickness 1.00 × 10^{-4} cm. The index of refraction of the oil is 1.25 and that of the glass is 1.50. Find the wavelengths of light in the visible region (400 nm-750 nm) which are completely transmitted by the oil film under normal incidence.

Consider the arrangement shown in figure (17-E7). By some mechanism, the separation between the slits S_{3} and S_{4} can be changed. The intensity is measured at the point P which is at the common perpendicular bisector of S_{1}S_{2} and S_{3}S_{4}. When , the intensity measured at P is I. Find this intensity when z is equal to

HC Verma - Concepts of Physics Part 1

In a Young’s double slit experiment λ = 500 nm, d = 1.0 mm and D = 1.0 m. Find the minimum distance from the central maximum for which the intensity is half of the maximum intensity.

HC Verma - Concepts of Physics Part 1The line-width of a bright fringe is sometimes defined as the separation between the points on the two sides of the central line where the intensity falls to half the maximum. Find the line-width of a bright fringe in a Young’s double slit experiment in terms of λ. d and D where the symbols have their usual meanings.

HC Verma - Concepts of Physics Part 1A soap film of thickness 0.0011 mm appears dark when seen by the reflected light of wavelength 580 nm. What is the index of refraction of the soap solution, if it is known to be between 1.2 and 1.5?

HC Verma - Concepts of Physics Part 1Figure (17-E5) shows three equidistant slits being illuminated by a monochromatic parallel beam of light. Let BP_{0} - AP_{0} = λ/3 and D >> λ. (a) Show that in this case . (b) Show that the intensity at P_{0} is three times the intensity due to any of the three slits individually.

HC Verma - Concepts of Physics Part 1

Consider the arrangement shown in figure (17-E4). The distance D is large compared to the separation d between the slits. (a) Find the minimum value of d so that there is a dark fringe at O. (b) Suppose d has this value. Find the distance x at which the next bright fringe is formed. (e) Find the fringe-width.

HC Verma - Concepts of Physics Part 1