Two Beam Interference by Fresnel Mirror

The Fresnel mirror is operated using grazing light incidence, whereby one mirror is tilted by approx. 1°- 2° with respect to the light beam. After adjusting the light source so that both mirrors are illuminated with equal luminous intensity, the inclination of the two reflected light beams can be adjusted with respect to each other by turning the knurled screw. The wavelength (λ) can be determined by the formula

Features:

• Heavy, rigid and stable Optical bench (made of Al extrusion)
• Saddle can hold rod from 8 to 15mm.
• Height and level adjustment screws (made of SS)
• He-Ne Laser have built-in power supply.
• Fresnel mirror with fine adjustment for one mirror (0 to 2°)

Objectives:

• To generate two virtual, coherent light sources through reflection of a point-shaped source at a Fresnel’s mirror.
• To observe interference of the virtual light sources.
• To determine the wavelength of He-He laser using Fresnel’s mirror.

Technical Data:

• Optical bench : Al extrusion, L = 1.5 mtr. with scale, Triangular shape with end stop, 4 point levelling (steel screw)
• Fresnel mirror : Size 45 x 50mm each, angle1-3
• Lens : FL 200mm, dia. 50mm
• Laser : He-Ne Laser (632mm), Power 2 mW, Beam spot 2.5mm, current 4mA ~ 6mA, Dimension 300 x 62 x 82mm, Weight 1.5 kg (approx.)
• Beam expender : Microscope objective, 10x
• Screen : Acrylic(translucent) 300 x 300 x 3mm
• Cylindrical base : Ferrous metal, 1 Kg
• Vernier caliper : 0 – 120mm, LC 0.01mm
• Optics Holder : Al, Dia. 130 x 3mm (Ø x T), H 230mm
• Transversal slider : 25 – 0 – 25mm, LC 0.01mm

Scope Delivery:

• 1 Optical bench triangular
• 1 Convex lens in holder
• 1 Transverse slider
• 1 Fresnel mirror
• 1 Objective holder
• 1 Screen
• 1 Cylindrical base
• 1 Vernier caliper
• 1 Measuring tape
• 1 He-Ne laser 2mW
• 1 Fixed slider
• 1 Extension arm
• 1 Beam expender
• 1 Fixed slider (large width)

Key Topics:

• Interference.
• Coherent sources by refraction.
• Virtual light source.
• Virtual coherent source by reflection refractive index.
• Fresnel mirror.
• Wave length.