Newton's Rings Apparatus

Model: HO-ED-INT-01

In this apparatus, light from a sodium lamp falls on the glass plate, inclined at 45 degree to the horizontal, get reflected, and then falls normally on the convex lens placed over the glass plate. A system of bright and dark concentric circular rings are observed through a microscope, arranged vertically above the glass plate. The microscope is properly focused so that alternate bright and dark concentric circular rings are observed more clearly. Measurements are taken from a micrometer driven traveling microscope, which is integrated with this apparatus.

The two interfering beams, derived from a monochromatic source satisfy the coherence condition for interference. Ring shaped fringes are produced by the air film existing between the convex surface of a long focus planoconvex lens and the plane of glass plate.

Experiment Examples

To determine the wavelength of Sodium light and LEDs ( Red, Blue, Green, Yellow )

Let Dm and Dm+k be the diameters of the mth and (m+k)th dark ring respectively. Then,

D2m  =  4 mRλ

D2 m+k  =  4 (m+k) Rλ

D2 m+k  -  D2 m  =  4 kRλ

λ  =  [D2 m+k  -  D2 m] / 4kR

where λ is the wavelength used and R is the radius of curvature of the lens.

To find the refractive index of liquid

Refractive index of liquid,

n  =  mλr / r^2

where, m order of the fringe, R Radius of curvature of the lens

λ wave length of light, r radius of the ring

To find the diameter of thin wire or thickness of a thin strip of paper using air wedge method

The diameter or thickness of the wire,

d  =  lλ / 2β

λ is the wavelength of the light

β is the bandwidth

l is the diameter of the wire or thickness of a thin strip of paper from the line of contact of the two plates of the air wedge.

Fig: Newton’s Rings Setup

Specifications    (Travelling Microscope)

Magnification : 10 X

Micrometer travel : 25 mm

Least count : 0.01 mm

Related Topics

Interference of light

Constructive Interference

Destructive interference

Refractive index

Boy's method
Features

Sodium vapor lamp and spectral LED's are used as light sources

Traveling microscope with precision micrometer is used for accurate measurements

The optics used in this device are of research quality

All materials used in this setup are of laboratory grade and are corrosion resistant
Scope of Supply

Travelling Microscope with Rigid Base

Model No: ED-INT-01-TMRB
Magnification
:
30 x
Micrometer Travel
:
25 mm
Least Count
:
0.01 mm
Quantity
:
1 no.

Lens Holder with Rigid Base

Model No: ED-INT-01-LHRB
Height
:
180 mm
Material
:
Anodized Aluminum Alloy & SS
Quantity
:
1 no.

LED Mount with Rigid Base

Model No: ED-INT-01-LEDM
Height
:
225 mm
Material
:
Anodized Aluminum Alloy & SS
Quantity
:
1 no.

Plano Convex Lens

Model No: ED-INT-01-PCL1000
Material
:
Borofloat
Diameter
:
50 mm
Focal Length
:
1000 mm
Quantity
:
1 no.

Plano Convex Lens

Model No: ED-INT-01-PCL750
Material
:
Borofloat
Diameter
:
50 mm
Focal Length
:
750 mm
Quantity
:
1 no.

Optical Flat

Model No: ED-INT-01-OF
Material
:
Borofloat
Diameter
:
50 mm
Quantity
:
1 no.

Beamsplitter Plate

Model No: ED-INT-01-BSP
Material
:
Borofloat
Diameter
:
45 x 45 mm
Quantity
:
1 no.

Sodium vapor lamp with Power Supply

Model No: ED-INT-01-SLPS
Output Power
:
35 W
Quantity
:
1 no.

LED's with Power supply

Model No: ED-INT-01-LEDP
Colours
:
Red, Blue, Green, Yellow
Out put
:
5V, 800 mA
Quantity
:
1 no. each

Accessories

Dust Protective cover
Instruction Manual