Optics Answers

A thin film of glass of refractive index 1.5 is inserted in one arm of Michelson
Interferometer. Calculate the thickness of the film if a shift of 10 fringes is observed.
The wavelength of the light used is 589 nm.

Newton’s rings are formed with reflected light of wavelength 589 nm using a plano-
convex lens and a plane glass plate with a liquid between them. The diameter of the
15th ring is 5.1 mm and radius of curvature of the curved surface of the lens is 1 m.
Calculate the refractive index of the liquid if the ring is dark.

Unpolarised light is incident on two polarizing sheets placed over one another. The
intensity of light transmitted finally is one-third of the intensity of the incident light.
Calculate the angle between the transmission axes of the two polarizing sheets.

The wavelength of the electromagnetic wave used for AM broadcasting is 110 m.
Calculate the frequency of the wave.

State Fermat’s principle. On the basis of this principle, show that when light passes
from a medium of lower refractive index to a medium of higher refractive index, it
bends towards the normal to the interface between the two media.

An insect is placed at the base( at centre ) of a cylindrical vessel and oil of refractive index u =2 is filled upto 10cm then water is poured in vessel upto height 20cm (length of water column 10cm ) if a convex lens of focal length 50cm is placed just above the surface of water then find the location of final image of the insect by this system if the insect starts moving up with speed 18m/s then what will be the speed of the final image just after its leaves the bottom

The wavelength of light diminishes n times ( n= 1.33 for water) in a medium.A driver from inside water looks at an object whose natural colour is green .He sees the object as
(1) green
(2) blue
(3) yellow
(4) red

A ray of light is incident at angle 60° on one face of a prism which has an apex angle of 30° . The ray emerging out of the prism make an angel of 30° with the incident ray . The refractive index of the material of prism is
(1)√2 (2)√3. (3)1.5 (4) 1.6

A square ABCD of side 1mm is kept at distance 15cm infront of the concave mirror . The focal length of the concave mirror is 10cm . The length of the perimeter of its image will be (1)8mm. (2) 2mm (3)12mm (4)6 mm

If a biconvex lens of power P is cut into 3 parts horizontally , then power of each part is?