Common Detailed Writng

Ramsden’s eyepiece

Trisha Banerjee_bhu @2010

An eyepiece is a magnified designed to give more perfect image than obtained by
single lens.
Construction of Ramsden’d eyepiece:-
This eyepiece consists of two plano convex lenses with their convex faces
turned inwards and separated by a distance equal to 2/3 f where f is their
common focal length . The lens facing the field is called the field lens and the other
close to the eye is called the eye lens.
Why Ramsden’s eyepiece is used with telescope:-
Because in it, cross wires are fitted outside the eyepiece and hence
mechanical adjustments and measurement are easily possible.
Where are cross wires situated:-
when the instrument is in normal position the cross wire lie at f/4 in front
of the field lens. It is the place where the real image is formed by the objective of
the telescope.

there are another type of eye piece is HUYGEN’S eyepiece.


Screw Gauge
Sleeve(Mai
anvil spindle n scale)
Thimble(Cir Rachet
Space to cular scale) knob
put the
object

frame


MSR = 5.2 + CSR = 42 MSR = 5.2 +CSR = 28


Jaws (
measure
Vernier Callipers
inner Screw
dimension) clamp

Main scale

Vernier
scale
Jaws ( measure
outer dimension)


Spectrometer


Spectrometer :- it is an impt instrument used for the study of
spectra produced by the prism and gratings, for the measurement of
the dispersive powers , wavelength of spectral line s, the refractive
indices of solid and liquids , etc.

The essential parts are:-

1)collimator
2) turn table
3) telescope


Collimator source

Vertical Achromatic convex
adjustable lens
slit

Sliding tube


Setting of the collimator
and the telescope


Collimator:-
It is a fixed horizontal metallic tube fitted with an achromatic convex
lens L1 at one end. At the other end it carries a shorter coaxial tube which
slides inside the longer tube. The end of the shorter tube carries a vertical
slit of adjustable width. The distance between the slit and the lens L1 can be
altered by a rack and pinion arrangement . The collimator is also provided
with leveling screws.


Turn Table
Turn
table

Vernier
scale

Screw to
rotate the
turn table Vernier scale
minutely
Lock the
telescope

Lock the
turn table


Turn Table:-
It is a circular table provided with a platform G on which the prism
is placed . The platform can be raised to a suitable height and can be
rotated along with the turn table about the axis of the spectrometer .
The rotation of the table can be measured by noting the position of two
vernier V1 and V2 on a circular scale. Parallel lines and concentric
circles are drawn on the platform . They help in placing the prism in the
desired position . The platform is provided with three leveling screws ,
while the table is provided with clamping and tangent screws.


Telescope
Achromatic
Ramsdens’s
convex lens
Sliding eyepiece
tube

Screw for adjusting the
length for focusing


Telescope:-
It is a horizontal metallic tube having an achromatic convex lens L2 at
one end . At the other end it carries a shorter coaxial tube containing cross
wires . Within this tube slides another small tube containing a Ramsden’s
eyepiece . The distance between the lens L2 and the cross wires can be
altered with a rack and pinon arrangement while that between the cross
wires and the eyepiece can be altered by hand . The telescope can be
rotated about the axis of the spectrometer and is provided with leveling
screws as well as with clamping and tangent screw. Its position can be read
on the circular scale.( which is attached to it) by means of verniers V1 and
V2.


Ballistic
galvanometer:-
galvanometer:-


Inner structure of galvanometer


Brief construction :-

The ballistic galvanometer is usually employed to measure the quantity of charge flowing in a given circuit
due to transient current.
it consists of a coil of copper wire wound on a non conducting frame which is suspended by a phosphor bronze strip
between the poles of strong permanent magnet horse – shoe shape magnet . In order to increase the magnetic flux
in the gap , the cylindrical soft iron – core is placed with in the coil. The pole pieces of the magnet are cylindrical
concave in shape so that the magnetic field is radial in the narrow annular gap and is also perpendicular to the coil
surface . The whole apparatus is covered in a shell to avoid disturbance from outside .Three leveling screws are
provided below the base of the galvanometer . The deflection of the coil is measured by lamp and scale arrangement
.

Note:- When large damping is present , the motion of the coil is non oscillatory and the moving coil galvanometer
become dead beat . The construction and working of such a galvanometer is different from moving coil
galvanometer.


Digital
multimeter


A digital multimeter:-

Multimeters contain Ohmeters, Voltmeters, Ammeters and a variety of capabilities to
measure other quantities. AC and DC voltages are most often measurable. Frequency
of AC voltages. Multimeters also feature a continuity detector, basically an Ohmmeter
with a beeper if the multimeter sees less than 100 Ω then it beeps otherwise it is silent.
This is very useful for finding whether components are connected when debugging or
testing circuits. Multimeters are also often able to measure capacitance and
inductance. This may be achieved using a Wien bridge. A diode tester is also generally
onboard, this allows one to determine the anode and cathode of an unknown diode. A
LCD display is also provided for easily reading of results.


Screen ( contains the
eyepiece) Ramsden’s
eyepiece

Main scale
Leveling the reading
vertical Micrometer
height of reading
the screen


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