The slits in a double-slit interference experiment are illuminated by orange light (λ = 60 nm). A thin transparent plastic of thickness t is placed in front of one of the slits. The number of fringes shifting on screen is plotted versus the refractive index μ of the plastic in graph shown in fig. The value of t is



Correct option is

24 μm


N = no. of fringes shifted 

Shift of central maxima = nλ = (μ – 1)t




The fringe-width is obtained as 0.060 cm on using light of wavelength 5000Ã… in Young’s experiment. What value of wavelength of light should be taken so that the width of the fringe on the screen could be obtained as 0.040 m, if the distance of screen from the slit is halved?



In a two-slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by  towards the slits, the change in fringe-width is . If the distance between the slits is 10–3 

M, calculate the wavelength of the light used. 


In Young’s experiment the interval between the slits is 0.200 mm. For the light of wavelength 600 mμ, interference fringes are formed on a screen at a distance of 80.0 cm. (i) What is the distance of the second dark fringe from the central fringe? (ii) What is the distance of the second bright fringe from the central fringe?   


Microwave from a transmitter are directed normally towards a plane reflector. A detector. A detector moves along the normal to the reflector. Between positions of 14 successive maxima the detector travels a distance 0.14 m. The frequency of the transmitter is (c = 3 × 108 m/s)    


In a Young’s double-slit experiment, the separation between the slits is d, distance between the slit and screen is D(D >> d). In the interference pattern, there is a maxima exactly in front of each slit. Then, the possible wavelength(s) used in the experiment are  


In a double-slit experiment, two parallel slits are illuminated first by light of wavelength 400 nm and then by light of unknown wavelength. The fourth-order dark fringe resulting from the known wavelength of light falls in the same place on the screen as the second-order bright fringe from the unknown wavelength. The value of unknown wavelength of the light is 


Light is incident at an angle Ï• with the normal to a plane containing two slits of separation d. Select the expression that correctly describes the positions of the interference maxima in terms of the incoming angle Ï• and outgoing angle θ.



In Young’s double-slit experiment, the slits are illuminated by monochromatic light. The entire set-up is immersed in pure water. Which of the following act cannot restore the original fringe width?


Blue light of wavelength 480 nm is most strongly reflected off a thin film of oil on a glass slab when viewed near normal incident. Assuming that the index of refraction of the oil is 1.2 and that of the glass is 1.6, what is the minimum thickness of the oil film (other than zero)?


In a YDSE with identical slits, the intensity of the central bright fringe is . If one of the slits is covered, the intensity at the same point is