wavelenght of sodium light using newton rings
EXPERIMENT: 1
Object: To find the wavelength of Sodium light by Newton’s ring.
Apparatus required: A Plano convex lens of large radius of curvature, optical arrangement for Newton’s rings, plane glass plate; sodium lamp and traveling microscope. Formula used: The wavelength of light is given by the formula λ =D n2+p –Dn2 / 4pR
Where D n+p = diameter of (n+p)th ring
Dn = diameter of n th ring,
P = an integer number,
R = radius of curvature of the curved face of the Plano- convex lens.
Procedure:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
If a point source is used only then we require a convex lens otherwise while using an extended source, convex lens L1 is not required.
Before starting the experiment the glass plates G1 and G2 and the plano convex lens should be thoroughly cleaned.
The centre of lens L2 is well illuminated by adjusting the inclination of glass plate G1 at 45.
Focus the eyepiece on the cross-wire and move the microscope in the vertical plane by means of rack and pin on arrangements till the rings are quite distinct.
Clamp the microscope in the vertical side.
According to the theory, the centre of the interference fringes should be dark but sometimes the centre appears white. This is due to the presence of dust particles between glass plates G2 and plano-convex lens L2. In this case the lens should be again cleaned.
Move the microscope in a horizontal direction to one side of the fringes. Fix up the crosswire tangential to the ring and note this reading. Again the microscope is moved in the horizontal plane and the cross wire is fixed tangentially to the successive bright fringes noting the vernier readings till the other side is reached.
This is shown in fig. (2)
The radius of curvature of the plano-convex lens is determined by Boy’s method as discussed below:
If an object is placed at the principal focus of convex lens placed over a plane mirror, its image is formed at same point and the distance from the lens is
Object: To find the wavelength of Sodium light by Newton’s ring.
Apparatus required: A Plano convex lens of large radius of curvature, optical arrangement for Newton’s rings, plane glass plate; sodium lamp and traveling microscope. Formula used: The wavelength of light is given by the formula λ =D n2+p –Dn2 / 4pR
Where D n+p = diameter of (n+p)th ring
Dn = diameter of n th ring,
P = an integer number,
R = radius of curvature of the curved face of the Plano- convex lens.
Procedure:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
If a point source is used only then we require a convex lens otherwise while using an extended source, convex lens L1 is not required.
Before starting the experiment the glass plates G1 and G2 and the plano convex lens should be thoroughly cleaned.
The centre of lens L2 is well illuminated by adjusting the inclination of glass plate G1 at 45.
Focus the eyepiece on the cross-wire and move the microscope in the vertical plane by means of rack and pin on arrangements till the rings are quite distinct.
Clamp the microscope in the vertical side.
According to the theory, the centre of the interference fringes should be dark but sometimes the centre appears white. This is due to the presence of dust particles between glass plates G2 and plano-convex lens L2. In this case the lens should be again cleaned.
Move the microscope in a horizontal direction to one side of the fringes. Fix up the crosswire tangential to the ring and note this reading. Again the microscope is moved in the horizontal plane and the cross wire is fixed tangentially to the successive bright fringes noting the vernier readings till the other side is reached.
This is shown in fig. (2)
The radius of curvature of the plano-convex lens is determined by Boy’s method as discussed below:
If an object is placed at the principal focus of convex lens placed over a plane mirror, its image is formed at same point and the distance from the lens is