Let S₁ and S₂ be the two slits in Young’s double slit experiment. If central maxima is observed at P and angle  then the fringe width for the light of wavelength λ will be. (Assume θ to be a small angle)

Figure shows two coherent sources S1-S2 vibrating in same phase. AB is an irregular wire lying at a far distance from the sources S1 and S2.  How many bright spots will be seen on the wire, including points A and B. 

If the ratio of the intensity of two coherent sources is 4 then the visibility [(I_max-  I_min)/(I_max+  I_min)] of the fringes is

In Young’s double slit experiment, we get 60 fringes in the field of view of monochromatic light of wavelength 4000 A⁰. If we use monochromatic light of wavelength 6000 A⁰, then the number of fringes that would be obtained in the same field of view is :

If the distance between the first maxima and fifth minima of a double slit pattern is 7mm and the slits are separated by 0.15 mm with the screen 50 cm from the slits, then wavelength of the light used is

The path difference between two interfering waves at a point on the screen is λ/6. The ratio of intensity at this point and that at the central bright fringe will be : (Assume that intensity due to each slit is same)

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 for each slit. Then the possible wavelengths used in the experiment are :

A point source of light is kept at the centre of a solid transparent sphere. The sphere is surrounded by air . The refractive index of material of sphere for which the rays incident from point source on glass–air interface will suffer total internal reflection is:

A point object ' O ' is at the centre of curvature of a concave mirror. The mirror starts to move at a speed u, in a direction perpendicular to the principal axis. Then the initial velocity of the image is:

In the figure shown an object ‘AB’ makes small angle with the normal line ‘PQ’. The length of ‘AB’ is l. The refractive index of the slab is ‘n’ and the surrounding medium is air. ‘AB’ is seen with the help of paraxial rays, from the left side of the slab. The size of the image of AB is