The experimental arrangement is shown in Figure 1. A plano-convex lens of large radius of curvature R is placed on a plane glass plate with its curved surface downwards and is illuminated from above with a parallel beam of monochromatic light. Some of the light is reflected from the upper surface of the glass plate and some from the lower surface of the lens; interference thus occurs by division of amplitude, the fringes being localised in the air gap between the lens and plate.
The beams produced from the monochromatic source satisfy the condition of coherence for interference. The dark and light fringes which are of ring shaped are produced by the air film existing between a plano-convex lens and a plane glass.
Although this phenomenon was first observed by Robert Hooke in According to the principle of superposition of waves — When two or more waves of same type are Wavelenght of sodium light using newton at the same point then the total displacement at that point is equal to the vector sum of the displacements of the individual waves.
The superimposing waves can have constructive or destructive interference. When crest of the first wave falls on the crest of second wave and trough of the first wave falls on the trough of the second wave and then the resultant wave is the vector sum of the amplitude of the two superimposing waves which is equal to sum of the amplitude of two waves, this is known as Constructive Interference.
When crest of the first wave falls on the trough of second wave and trough of the first wave is falls on the crest of the second wave and the resultant wave is the vector sum of the amplitude of the two superimposing waves which is equal to the difference in amplitude of two waves, this is known as Destructive Interference.
Because of the constructive interference between the light rays reflected from both surfaces, light rings are formed while the dark rings are formed because of the destructive interference.
Let, the ray now strikes the upper surface of the air film nearly along the normal. The ray is partly refracted in the air film and also partly reflected at the lower surface of the film.
The reflected rays which are produced at the upper and lower surface of the film, are coherent and interfere constructively or destructively. The light which is reflected upwards if seen through the microscope M which is focused on the glass plate, it is observed that the series of dark and bright rings are seen with each of them centered at O.
Fig 6 R is the radius of the circle O is the center of the circle AC is the diameter r is the distance between D and E from the center B. For the points D and E to lie on a bright fringe Using any of the two relations, we can find the wavelength of the monochromatic light used.
Formula Used To find the radius of curvature of the convex lens where l is the distance between the two legs of the spherometer and h is the height or the thickness of the lens at the center.
To find the wavelength of sodium lamp used How to use Spherometer Fig 7: Images of Spherometer 1. A Spherometer is an instrument used to measure the radius of a spherical surfaces. A Spherometer consists of a linear scale, a circular scale marked on a circular disc at the top, three legs which form the vertices of an equilateral triangle and a middle leg which is movable.
Pitch is the linear progress made by the circular scale on the main scale in one complete rotation. Pitch of the spherometer can be determined by rotating the circular scale and checking the distance covered by it on the main scale in one rotation.
Least count is the least possible measurement that can be taken with the help of an instrument. Least count is the resultant of the pitch calculated divided by the total no.
Nowto calculate the distance between the three legs of the spherometer place it on a paper applying some pressure, you will see the imprints of three legs, join them and measure the distance using scale. After measuring all the three sides take the mean of all the three sides.
To measure the radius of curvature of a spherical surface: Place the spherometer on the surface. Rotate the middle leg till it just touches the spherical surface and note the linear scale and circular scale reading.
Now place the spherometer on a flat surface. Again rotate the middle leg till it just touches the flat surface and note the main scale and circular scale reading. Radius of curvature can be calculated using the formula where l is the distance between the two legs of the spherometer and h is the height or the thickness of the lens at the center.
Place the lens L at a distance equal to its focal length from the sodium lamp to get a parallel beam of light. Adjust the microscope vertically above the center of the lens. Focus the microscope so that alternate dark and light rings are clearly visible. Note the main scale and circular scale readings present on the microscope in both the cases.
Now again do the same for the same set of dark ring.
Record the observed values. Find the difference of the values observed for the same left and the right ring. Take the mean of the two differences calculated.
The result is the diameter of ring formed. Repeat the procedure no. Record the observed values in a table.
Now, take out the convex lens and the plane glass out from the case carefully and measure the radius of curvature of the convex lens and also the height of the convex lens with the help of the spherometer. Plot the graph between the no. Observations For Radius of curvature R:Newton's rings is an interference pattern caused by the reflection of light between two surfaces - a spherical surface and an adjacent flat surface.
EXPERIMENT: 4 Object: To find the wavelength of Sodium light by Newton’s ring. Apparatus used: A Plano convex lens of large radius of curvature, optical arrangement for Newton’s rings, plane glass plate, sodium vapour lamp and traveling microscope. Determination of 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 fo r Newton's rings, plane glass plate; sodium lamp and .
Aim To determine wavelength of sodium light using Newton’s Rings. Apparatus Required Newton's rings apparatus, travelling microscope, sodium lamp, a convex lens and a spherometer.
Introduction Newton's Ring is the demonstration of the interference of light waves reflected from the surface of a thin air film formed between the plane glass and . Experiment8. To Determine the Wavelength of Sodium Light using Newton’s Rings Table Sample data table Ring Number Lm j Lm - L1j Rm j Rm - R1j Dm 24 23 1 Spherometer A spherometer is used to ﬁnd R, the radius of curvature of the lens.
Using a Compound Light Microscope Purpose: The purpose of this lab is to 1. Learn the parts of a compound light microscope.
2. The functions of those parts. 3. Proper use and care of the microscope. 4. Learn the technique of preparing wet-mount slides.