LABORATORY MANUAL

PHYSICS
GRADE XII

NAME:
CLASS & R.NO:

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2
CONTENTS
SECTION A

EXPERIMENTS

1. OHM’ S LAW

2. METRE BRIDGE-I (UNKNOWN RESISTANCE)

3. METRE BRIDGE-II (LAW OF COMBINATION OF RESISTANCE)

4. SONOMETER AC FREQUENCY

ACTIVITIES

ACTIVITY 01-MULTIMETER

ACTIVITY 02-HOUSEHOLD CIRCUIT

ACTIVITY 03- CONSTRUCTING AN ELECTRICAL CIRCUIT

SECTION B

1. FOCAL LENGTH OF CONCAVE MIRROR

2. FOCAL LENGTH OF CONVEX LENS

3. PRISM MINIMUM DEVIATION

4. PN JUNCTION DIODE

ACTIVITIES

ACTIVITY 04- COMBINATION OF LENS

ACTIVITY 05- REFRACTION THROUGH GLASS SLAB

ACTIVITY 06- IDENTIFICATION OF SEMICONDUCTOR DEVICES

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 ACTIVITY 01-MULTIMETER
AIM :
To use a multimeter for:
(i) Continuity test of a cartridge fuse, a slide wire bridge and a potentiometer,
(ii) Finding the d.c. voltage of different tappings on the energized battery eliminator.
(iii) Finding the output a.c. voltage of a step down transformer (250V-6V)

APPARATUS REQUIRED:
A multimeter, a cartridge fuse, a slide wire bridge, a potentiometer, battery eliminator, a
step-down transformer (250V-6V), a junction diode and an LED.
PROCEDURE:
1. Continuity test
(i) Insert the probes such that black is in terminal marked common on the multimeter and the
red in terminal marked (+). Selector switch should be turned on to continuity check. Insert
the cartridge fuse in between the metallic ends of the probes such that the probes touch
the metallic ends of the fuse. A beep sound from the multimeter indicates continuity of the
cartridge.
No sound from the multimeter indicates the fuse wire is broken as the gap offers extremely
high resistance. We say, there is a discontinuity in the fuse.
(ii) Now replace the cartridge fuse by the wire of the slide wire bridge and test its continuity.
(iii) Repeat step (ii) again by inserting potentiometer wire in between the probes to test its
continuity. The multimeter shows the value of resistance which is an indicator of the
continuity of the potentiometer wire.

2. D.C Voltage Measurements

(i) Set the selector switch on the multimeter to D.C voltage in the range of (0 to 10V)
(ii) Keep the tapping of the battery eliminator connected to the mains to the minimum and
insert the metallic end of the red probe in the positive terminal of the eliminator. Observe
the deflection on the scale marked D.C. voltage (0-1-V).Note the D.C. voltage.
(iii) Shift the tapping of the eliminator to the next higher value and read the D.C. voltage again.
(iv) Repeat the above for other tapping of the battery eliminator. Note the voltage in each case.
(v) Compare the readings written on the eliminator with the observed values in each case.
(vi) You may do the experiment by taking different cells e.g. dry cell, Leclanche cell, Daniel cell,
battery etc. or by combining cells in series.

3. A.C. voltage Measurement

(i) Set the selector switch of the multimeter to the a.c. voltage in the voltage range of 0-10V.
(ii) insert the metallic end of the black probe of the multimeter into the terminal marked common
and that of the red end probe into the terminal marked positive(+).
(iii) Switch on the transformer by connecting its primary to the mains of an a.c. supply. Touch the
metallic ends of the two probes to the ends of the secondary of the transformer. Read the a.c.
voltage on the proper scale of the multimeter

RESULT:
The given fuse is continuous/ discontinuous.
The measured dc voltage is ___________ V
The measured ac voltage is ___________ V

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 ACTIVITY 02-HOUSEHOLD CIRCUIT
AIM: To assemble a household circuit, comprising three bulbs, three (on/off) switches, a fuse and a
power source.
APPARATUS REQUIRED: Three bulbs(20W), three (on/off) switches, a fuse wire, a two-pin socket,
flexible connecting wires with red and black plastic covering, a piece of
sand paper , an insulating tape, a tester, main electric board with a two
pin socket and a main switch.

PROCEDURE
1. Connect one end of the bulb-holder to the red wire and the other end to the black wire through
a wire.
2. Now connect the three bulbs in parallel combination as shown in figure in such a way that the
red wire ends at one point and the black wire at the other point.
3. Also take two long flexible wires to serve as lead wires. Join the red wire ends to the red lead
wire (L1), serving as live-lead.
4. Join the black wire ends to the black lead wire (L2), serving as neutral lead.
5. Connect these leads to the power supply

RESULT
The household parallel circuit is constructed and checked.

PRECAUTIONS
1. Draw a circuit diagram and get it checked by the teacher before connecting the final circuit
2. The ends of the wire should be cleaned with a sand paper.
3. Make neat and tight connections
4. Ensure that all the marked joints are properly covered with insulating tape.
5. The end points of the leads L1 and L2 should be confirmed.

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 ACTIVITY 03- CONSTRUCTING AN ELECTRICAL CIRCUIT

AIM: To assemble the components of a given electrical circuit.

APPARATUS REQUIRED:
A metallic conductor (say a coil or a resistance wire), an ammeter, a voltmeter of suitable range, a cell
or a battery, a rheostat, a one way key, a piece of sand paper and some connecting wires

PROCEDURE

1. Draw the circuit diagram as shown above

2. Now arrange the apparatus in the same way as done in the arrangement diagram
3. Clean the ends of the connecting wires using the sand paper to establish a proper contact by
removing insulations
4. Make neat and tight connections as given in the circuit diagram
5. Ensure that the terminals of ammeter and voltmeter marked (+) are connected to the terminal
of the cell or battery

RESULT: A circuit is constructed using the given components and tested.

PRECAUTIONS

1. The connections should be neat, tight and clean.

2. The rheostat should have low resistance.
3. The voltmeter and ammeter should be of proper range.
4. The key should be inserted only while recording observations.
5. Tight connecting wires must be used for establishing connections in the circuit.

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(TO BE WRITTEN ON THE LEFT SIDE OF THE RECORD)
CIRCUIT DIAGRAM

MODEL GRAPH

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EX.NO:1A OHM’S LAW DATE:
AIM:
To determine resistivity of two wires by plotting a graph for potential difference versus
current.
APPARATUS:
Two pieces of high resistance wire about 1m long, a dc voltmeter, a dc ammeter, a rheostat,
plug key, battery eliminator, connecting wires, sand paper and a metre scale.
STATEMENT &FORMULA:
Ohm’s law states that at constant temperature, the current flowing through a conductor
varies directly as potential difference between its ends.
1. Resistance of the wire
𝑉
𝑅 = (Ω)
𝐼
where V is the potential difference (V) and I is the current (A).
2. Resistivity of the wire
𝑅𝐴
𝜌= (Ω𝑚)
𝑙
where R is the resistance of the wire (Ω), A is the area of cross section (𝑚2 ) and ‘l’ is
the length of the wire (m)

PROCEDURE:
1. The connections were made as shown in the circuit diagram. Voltmeter is connected in parallel
with the given wire, ammeter is connected in series.
2. Insert the plug key. Slide the contact point of the rheostat to one of its extreme positions such
that ammeter will show least current in the circuit. Note the values of current and voltage using
ammeter and voltmeter respectively.
3. Slowly slide the rheostat contact to the other extreme end in steps and record the values of
voltmeter and corresponding current I from ammeter
4. Remove the resistance wire from the circuit arrangement and stretch it along the meter scale.
Measure the length of the wire.
5. Measure the diameter of the resistance wire with a screw gauge
6. Plot V versus I graph for the wire.
7. Repeat the procedure for the second wire.

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PRELIMINARY OBSERVATIONS:
1. Range of the Ammeter : ______ A
2. Least count of the Ammeter : _______A
3. Range of the Voltmeter : _______V
4. Least count of the Voltmeter : _______V
5. Length of the given wire : 1._______m 2.______m
6. Diameter of the given wire : 1.________m 2. _____m

EXPERIMENT OBSERVATIONS:

S.NO VOLTMETER READING V(V) AMMETER READING I (A) RESISTANCE V/I R (Ω)

Wire(1)

Wire(2)

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RESULT:
1. The resistance of the given wire (1) from graph R= ----------------------------------- Ω
2. The specific resistance of the material of wire (1) =--------Ω m
3. The resistance of the given wire (2) from graph R= ------------------ Ω
4. The specific resistance of the material of wire (2) =--------Ω m

PRECAUTIONS:
1. Check the connections of the terminals of voltmeter and ammeter so that their positive
terminal must be connected towards the positive potential of the battery.
2. All connection must be rigid. Any loose connection introduces additional resistance 3. Insert
the plug key while making observations, otherwise the current flowing in the circuit cause
unnecessary heating effect
SOURCES OF ERROR:
(1) The connecting wires may not have negligible resistance.
(2) The ends of the wires may not be clean

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CIRCUIT DIAGRAM

OBSERVATIONS:

LEAST COUNT OF METRE BRIDGE=_______

S.NO KNOWN BALANCING LENGTH 𝑙

𝑅 = 𝑆 100−𝑙 (Ω)
RESISTANCE
S (Ω) 𝑙 𝑐𝑚 (100 − 𝑙) 𝑐𝑚

MEAN=__________ Ω

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EX.NO 2 A METRE BRIDGE –I DATE:

AIM:
To find the resistance of a given wire using a metre bridge

APPARATUS:
Metrebridge, given specimen wire, galvanometer, Leclanche cell, plug key resistance box, screw gauge,
connecting wires, jockey and sand paper

FORMULA:
The unknown resistance of the specimen wire
𝑙
𝑅=𝑆 (Ω)
100 − 𝑙

Where S = resistance in the resistance box (Ω)

‘𝑙’balancing length towards the unknown resistance ( cm)

PROCEDURE:
1. The connections were made as shown in the circuit diagram.
2. Check the direction of deflection of the galvanometer by pressing the jockey at one end of the metre
bridge, and then at the other end. If the galvanometer shows opposite deflections, the circuit connections
are correct
3. Adjust the value of R from the resistance box in such a way that the balance point is obtained nearly at
the middle of the metre bridge wire. Note the balancing length.
4. Repeat the experiment with different values of R

RESULT:

Resistance of the given wire R= ------------------------------------- Ω

PRECAUTIONS:
1. All connection must be rigid. Any loose connections introduce additional resistance
2. Use a high resistance if the deflection of the galvanometer is large.
3. The jockey should be pressed gently on the wire

SOURCES OF ERROR:
1. The entire length of the metre bridge wire may not be of uniform area of cross section
2. The screw gauge may have faults like back lash error and wrong pitch.

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CIRCUIT DIAGRAM

B
K

R1 R2
P

ℓ 100-ℓ

B-Battery or cell
K- Key
P-Known resistance
R1, R2 - Resistance wires.
G- Galvanometer
AC-Metre bridge wire
ℓ - Balancing length

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EXP.NO:03(A) DATE: __/__/__

METER BRIDGE-II (LAWS OF COMBINATION OF RESISTANCES)

AIM:
To verify the laws of combination (series/parallel) of resistances using a metre bridge.
APPARATUS:
Power supply/Battery, Meter Bridge, a resistance box, resistance wire, Screw gauge,
Galvanometer, Key, Rheostat and connecting wires.

FORMULA:

(a) Resistance of the wire R  P 
100 - 
Where S - Known resistance Ω ; l - Balancing length (cm)
(b) Sum of resistances in series 𝑅𝑆 = 𝑅1 + 𝑅2 Ω
𝑅 𝑅
(c) Sum of resistances in parallel 𝑅𝑃 = 𝑅 1+𝑅2 Ω
1 2

PROCEDURE:
01. Arrange the apparatus according to the circuit given above.
02. Connect the resistance wire whose resistance R1 is to be determined in the right gap. Take
care that no part of it forms a loop.
03. Take out some resistance (say 1 ohm) form the resistance box and plug the key K.
04. Touch the jockey gently first at left end and then at right end of the wire. Note the
deflections in the galvanometer. If the galvanometer shows deflections in opposite
directions, the connections are correct.
05. Slide the jockey gently along the wire from left to right till galvanometer gives no
deflection. It is the null point.
06. Measure the distance of this null point from the left end. It is equal to ‘l’.
07. Repeat the experiment by changing the value of R 1 to R2.
08. Record your observations.
09. Repeat the same experiment by keeping the resistances in series /parallel and record your
observations.
Using the formula, verify the laws of combination of resistances.

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EXPERIMENTAL OBSERVATIONS:
TO DETERMINE THE RESISTANCES R1&R2, RS&RP
Value of resistance P= ____ Ω

Balancing Balancing  Mean

R P 
Resistors length ℓ (cm) Length 100 -  R (Ω)
connected 100-ℓ (cm)

R1

R2

𝑅𝑆 = 𝑅1 + 𝑅2 Ω

𝑅𝑃
𝑅1 𝑅2
= Ω
𝑅1 + 𝑅2

CALCULATIONS:

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RESULT:
(a) The value of resistances R1 =________Ω & R2= ________Ω
(b) Sum of resistances in series R S =________Ω
(c) Sum of resistances in parallel RP =________Ω
PRECAUTIONS:
1. All connections should be tight.
2. The circuit should be switched off between the readings to maintain the constant
temperature.
3. All readings should be without parallax error.
4. The unused keys in the resistance boxes must be tightly fixed in their respective slots.
5. Null point should be brought between 40 cm and 60 cm on the bridge.
SOURCES OF ERROR:
1. The entire length of the metre bridge wire may not be of uniform area of cross section.
2. Error due to sliding of jockey on the wire.

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13
EXP.NO (4 A) DATE: __/__/__
SONOMETER –AC FREQUENCY
AIM:
To find the frequency of the AC mains using a Sonometer.
APPARATUS REQUIRED:
Sonometer, Step down transformer, Knife edges, an electromagnet, Slotted weights, paper
rider and connecting wires.
FORMULA:
The frequency of AC cycle is given
1 𝑇
𝜗 = 2𝐿 √𝑚 (Hz)
Where L is the length (cm), T is tension (N) and m is the per unit length of the stretched
wire(kg/m)
PROCEDURE:

1. Set up the sonometer and stretch the wire AB by placing a load of ½ kg on the hanger
2. Support the electromagnet in a stand and connect it to the secondary of a step down
transformer. Adjust its position, such that its one pole lies close to the middle of the sonometer
wire.
3. Switch on the alternating current supply and adjust the length of vibrating portion of AB by
sliding the wedge W or W′. Make this adjustment until the amplitude of the vibrating string is
maximum.
4. Measure the vibrating length and note the tension in the string.
5. Increase the load in steps of ½ kg and each time find the vibrating length.
6. Switch off the ac supply. Untie the wire of the sonometer from its peg and find its mass in a
physical balance. Calculate mass of 100 cm sonometer wire. Hence find the mass per unit length,
m for the wire.

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PRELIMINARY OBSERVATIONS:
Diameter of the wire=_________mm
Radius of the wire: ______mm=_______x10-3m.
Density of the material: ρ=--------- kg/m3
Mass per unit length: m=𝜋𝑟 2 𝜌

EXPERIMENTAL OBSERVATION:

S.No. Load M (kg) Resonating Length Tension √𝑻

N/m
(L cm) T=Mg 𝑳
(N)
L1 L2 Mean L

MEAN:________

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RESULT:
The frequency of AC mains=___________ Hz
PRECAUTIONS
1. Pulley should be as frictionless as possible.
2. Edges of the wedge should be sharp.
3. Tip of the electromagnetic pole should be close to the middle of the sonometer wire.
4. After taking each of the observations, circuit should be switched off for a few minutes.
SOURCES OF ERROR
1. Friction of the pulley is the main source of error in the experiment. Due to this, the value of
tension acting on the wire is less than that actually applied.
2. AC frequency may not be stable.

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FOCAL LENGTH OF CONCAVE MIRROR:

u-v method.

PRELIMINARY OBSERVATION:

Least count of optical bench=_________

Focal length of concave mirror by distant object method=_________

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EXP.NO:01(B) DATE: __/__/__
FOCAL LENGTH OF CONCAVE MIRROR
AIM:
To find the value of v for different values of u in case of a concave mirror and to
find the focal length.
APPARATUS REQUIRED:
Concave mirror, Stand, Screen, Illuminated wire gauze, Metre scale
FORMULA:
Focal length of the given concave mirror
1 1 1 𝑢𝑣
= + 𝑜𝑟 𝑓 = X 10- 2m
𝑓 𝑣 𝑢 𝑣+𝑢

where f is the focal length (cm), u is the object distance (cm)and v is image
distance.(cm)
PROCEDURE:
BY DISTANT OBJECT METHOD:
1. Fix the given concave mirror on the stand and place it on a table, facing towards a distant
object.
2. Arrange the screen on the table so that the image of the distant object is obtained on it.
3. Measure the distance between mirror and screen using a metre scale. It can be taken as
the focal length (f) of the mirror.
BY U-V METHOD :
1. Using the focal length obtained by distant object method set the values of u (distance
between mirror and object) ranging from 1.5f to 2.5f. Divide the range into a number of
equal steps.
2. Place the mirror in front of an illuminated wire gauze. It acts as the object.
3. Now, fix the mirror at the distance u (which is obtained as 1.5f) from the wire gauze.
4. Place the screen on the table facing the mirror in such a way that the reflected image lies
on the screen.
5. We can adjust the position of the screen to get the clear image of the wire gauze.
6. Keeping the distance between object and mirror fixed, adjust the position of screen in
order to get the clear image of the object.
7. Measure the distance between mirror and wire gauze, as well as mirror and screen. Take
these values as u and v respectively.
8. Record the values of u and v in a tabular column.
9. Calculate the focal length of the given concave mirror by using the relation, f = uv/(u+v).
10. Repeat the experiment for different values of u (up to 2.5f) and in each time, measure v
and record it in the tabular column.

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EXPERIMENTAL OBSERVATION:

MEAN:

CALCULATIONS:

Calculate the value of focal length (f) each time and find its mean.
Plot a graph with u along X axis and v along Y axis by taking same scale for drawing the X and Y
axes. Draw the bisector OA and join OC and OB. Thus, OC=OB= 2f. Calculate the focal length from
this.

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 1. Calculate the focal length (f) of the concave mirror each time.
2. Calculate the mean of all focal lengths to get the correct focal length of the given concave
mirror.
3. The focal length of the mirror can also be measured graphically by plotting graphs between
u & v, and 1/u & 1/v.
14. Calculate the focal length (f) of the concave mirror each time.
15. Calculate the mean of all focal lengths to get the correct focal length of the given concave
mirror.
16. The focal length of the mirror can also be measured graphically by plotting graphs between
u & v, and 1/u & 1/v.

RESULT:
The focal length of the given concave mirror, f

By u-v method = ……..×10-2 m

From u-v graph =.……..×10-2 m

PRECAUTIONS
1) While placing the distant object, the object should be clearly visible.
2) The image on the screen should be sharp and well defined.
3) While measuring all the distances the scale should be kept parallel to the ground.

SOURCES OF ERROR
1) The measuring scale may not be parallel to the base of both the stands.
2) The mirror holder, along with the mirror, may not be kept perpendicular to the measuring
scale.
3) Least count of measuring scale may not be correctly noted.
4) Measurement of distance from pole may not be made accurate.

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 Image
Needle

Object Image
Needle Needle

u v

PRELIMINARY OBSERVATIONS:
01. Rough focal length of the convex lens = __________ cm
02. Least count of the optical bench / metre scale = __________

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EXP.NO:02(B) DATE: __/__/__
FOCAL LENGTH OF CONVEX LENS
AIM:

To find the focal length of a convex lens by plotting graphs between u and v, and between 1/u
and 1/v.

APPARATUS REQUIRED:

Convex lens, Optical bench, object and image pins, meter rule

FORMULA:
1 1 1
  Or
𝑢𝑣
𝑓 = 𝑢+𝑣 𝑐𝑚
f u v

where f is the focal length, u is the object distance and v is image distance

PROCEDURE:

01. Find the rough focal length of the convex lens by focusing distant object on the wall or on
the screen.
02. Mount the convex lens with its holder on the central upright of the optical bench. Also
mount the two needles on the other uprights, one on each side of the lens so that tips of
the needles are at the same height as the optical centre of the lens.
03. Place the object needle at 0 cm. Place the lens at a suitable distance (Say between F and
2F). Look on the other side of the lens for the inverted image of the object needle.
04. Adjust the position of the image needle till the parallax is removed tip to tip between the
image needle and the image of the object needle. Note down the image distance.
05. Repeat the experiment by placing the lens at different distances from the object needle.
[4 object distances between F and 2F and 4 beyond 2F]
06. Choose a suitable but the same scale to represent u and v along x and y axes respectively.
Plot the points for various sets of values of u and v from the table.
07. The graph comes out to be a rectangular hyperbola.[Graph I]
08. Draw a line making 45 with either axis. This line meets the curve at (2f, 2f).
09. Choose a suitable but the same scale to represent 1/u along x – axis and 1/v along y axis.
10. Plot the points for the different sets of values of 1/u and 1/v. The graph is a straight line.
It cuts axes at points P and Q as shown in [Graph II].
11. Focal length f = 1 / OP = 1 / OQ.

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EXPERIMENTAL OBSERVATION

S. No. Object distance ‘u’ Image distance ‘v’ Focal length ‘f’
(cm) (cm) (cm)
1

v Q
cm

2
f 1/v
(m-1)

2 P
u
f 1/u (m-1)
(cm)
Graph I Graph II

CALCULATIONS:

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PRECAUTIONS:
1. The uprights supporting the optical elements should be rigid and mounted vertically.
2. The aperture of the lens should be small otherwise the image formed will not be distinct.
3. Eye should be placed at a distance more than 25 cm from the image needle.

SOURCES OF ERROR:

1. The uprights may not be vertical.

2. Parallax removal may not be perfect.
3. If the knitting needle or index rod for finding index correction is not sharp like a needle, its
length may not be accurately found on scale.
RESULT:
The focal length of the given convex lens as determined from
1. u &v graph = __________ cm (OR)
2. 1/u &1/v graph = __________ cm

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 ACTIVITY 04
COMBINATION OF LENS
AIM:
To obtain a lens combination with the specified focal length by using two lenses from the
given set of lenses.
APPARATUS REQUIRED:
Convex lenses of given focal lengths, screen, metre scale, optical bench with two uprights.
FORMULA:
Power of combination of lenses:
𝑃 = 𝑃1 + 𝑃2
The sum of focal length is given by:
1 1 1
= +
𝐹 𝑓1 𝑓2

PROCEDURE:
1. First find the approximate focal length of one of the lenses by making a sharp image of distant
object on the screen.
2. Then repeat the same process for the second lens as well.
3. Now place both lenses on uprights and adjust their positions so that you get a sharp image of
distant object on screen.
4. Measure the focal length of this system of lenses.
5. Verify the findings by calculating sum total of individual focal lengths.
RESULT:
The effective power of combination of lenses=________.D

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 ACTIVITY 05
REFRACTION OF LIGHT THROUGH GLASS SLAB

AIM: To observe refraction and lateral deviation of a beam of light incident obliquely on a glass
slab.
APPARATUS REQUIRED:
Sheet of white paper, glass slab, drawing board, two thin long knitting needles, metre scale, pencil
etc.

PROCEDURE
1. Fix a sheet of white paper on the drawing board with the help of cello tape of drawing pins.
Put the glass slab on it and mark its boundary ABCD with s sharp pencil.
2. Remove the slab from the sheet and draw an oblique straight line PQRS with the help of a
metre scale or a ruler intersecting shown in fig 2. Put the glass slab back on its drawn
boundary.
3. Place one of the knitting needles say KN, along the line PQ and look for its image on the other
side of the slab. Place the second needle RS in such a way that that the needle KN and its
image K’N’ lie in the same straight line.
4. Draw a straight line along the length of the needle RS. Observe the distance between the
incident ray and the emergent ray. You will find that the lines PW and K ’N’ which represent
ray and the emergent rays respectively are at a fixed distance from each other and are.
Therefore, parallel to each other but are laterally displaced.

RESULT
1. The ray of light emerging from glass slab is parallel to the incident light and it is laterally
displaced.
2. The angle of incidence is equal to angle of emergence.

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PRISM – MINIMUM DEVIATION

D
m

Q R

P S
B
C

PRELIMINARY OBSERVATIONS:
The least count of protractor = __________
The angle of prism ‘A’ = _________

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EXP.NO:03(B) DATE: __/__/__
PRISM – MINIMUM DEVIATION
AIM:
To determine the angle of minimum deviation for a given glass prism by plotting a graph between
the angle of incidence and angle of deviation.
APPARATUS: A Drawing board, a glass prism, a white sheet of paper, drawing pins, a pencil, a
scale, a graph paper, a protractor.
FORMULA:
The refractive index of the given material of the prism
(𝐴 + 𝐷)
𝑠𝑖𝑛
𝜇= 2 (no unit)
𝐴
𝑠𝑖𝑛 2

where A is the angle of prism and D is the angle of minimum deviation

PROCEDURE:
01. With the help of drawing pins, fix a white sheet of paper on the drawing board.
02. Divide the given sheet into 4 quadrants by drawing lines. At the centre of each quadrant,
keep the prism and draw its outline.
03. In the quadrant I, draw a normal N at the centre of the face as shown in the diagram.
04. Using a protractor, measure 30 and draw a line. Fix two pins P and Q vertically on this line.
The distance between the pins should be about 8 cm. Now view the images of P and Q from the
other side.
05. Fix two more pins R and S on the paper vertically and about 8 cm apart such that the tips of
these pins and the tips of the images of the incident ray pins P and Q, all lie on the same straight
line.
06. Remove the pins and join the points (pin pricks) R and S and produce it backwards to meet
the incident ray produced as shown in figure using dotted line. RS is the emergent ray
corresponding to the incident ray PQ.
07. Measure the angle of deviation D.
08. Repeat the steps 04 to 07 for angles 350, 400, ….650.
09. Record all the observations in the table.
11. Plot a graph between the angle of incidence and the angle of deviation.
12. Measure the angle of minimum deviation D m as shown in the graph.

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EXPERIMENTAL OBSERVATION:

S. No. Angle of Incidence (i) Angle of Deviation (d)

Angle of
deviation

Dm

Angle of
incidence

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PRECAUTIONS:
1. The angle of incidence should lie between 350to 600
2. The pins should be fixed vertical.
3. The distance between two pins should not be less than 5 cm.
4. Arrowheads should be marked to represent the incident and emergent Ray
5. The same Angle of prism should be used for all observations
SOURCES OF ERROR:
1. Pin pricks may be thick.
2. Measurement of angles maybe wrong.

RESULT:
The angle of minimum deviation, D m = __________

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31
 ACTIVITY 06
IDENTIFICATION OF SEMICONDUCTOR DEVICES

AIM :
To identify a diode, transistor, an IC (integrated circuit), a resistor and a capacitor from a mixed
collection of such items.
APPARATUS REQUIRED:
Diode, a transistor, an IC, a resistor and a capacitor.
THEORY:
Resistor, capacitor and diode are two terminal devices. A transistor has three terminals and an
IC has minimum of eight legs. Most of the IC packages have flat back. IC can easily be segregated
out of the given collection. A transistor can easily be identified by counting its legs - it has three legs
or three terminals.
The two terminal devices are identified by their characteristics.
Resistor:
A resistor when connected in any d.c. circuit (say ohm’s circuit) is identified by a constant
flow of current as shown by the ammeter connected in the circuit.
Capacitor:
A capacitor when connected in any d.c. circuit shows full scale deflection in multimeter set
at R which quickly decays to zero.
Diode:
A diode conducts only when forward biased and does not conduct when reverse biased as
explained before. A junction diode is forward biased when its p-type crystal is connected to the
(+ve) terminal of the battery and the n-type crystal is connected to the (-ve) terminal of the battery.
Therefore a junction diode conducts when forward biased and does not conduct when reverse
biased.
PROCEDURE:
1. From the mixed components identify the one with maximum number of legs. i.e. the component
which has more than 3 legs. This component should have a flat face with flat metal strip; legs and
the tips of legs are thinner than the top. This component is IC.
2. The component with three legs is a transistor.
Use a multimeter with selector switch turned on to position for checking its continuity. The probe
metal ends are inserted in terminals such that the black is in common and red probe is in +ve).
3. On touching the two ends of the device to the two other metal ends of probes, if there is
continuity in both the directions (directly connected and reversed i.e. a beep sound is heard, the
component is a resistor. Or, when the selector switch turned on to position for checking its
resistance, it reads the same value in both the directions.
4. When the device on connecting to the probes of the multimeter shows a full scale deflection to
begin with and then the deflection quickly decays to zero. (I.e. the device has very high or infinite
resistance), the device a capacitor.

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RESULT
A diode, a LED, a transistor, an IC, a resistor and a capacitor are identified respectively from a mixed
collection.
PRECAUTION
1. While obtaining resistance of any component, clean its leads properly.
SOURCES OF ERROR
1. When the metal ends of a multimeter leads are touched, the multimeter should show zero
resistance. If it does not show it, bring the pointer to zero using ‘Zero Adj knob’ on the multimeter.
If it is not done, the resistance measurements are not reliable.
2. While checking resistance of a component, avoid touching either of the metal ends of the
multimeter leads. Body resistance in parallel with component resistance can affect the resistance
measurement.

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CIRCUIT DIAGRAM:

S. NO. Voltage (Vf) Current (If)

(V) (mA)
S. NO. Voltage (Vr) Current(Ir)
1 V mA

1
2
2
3
3
4 4

5 5

6
6

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EXP.NO:06(B) DATE: __/__/__
PN JUNCTION DIODE
AIM: To draw the characteristic curves in forward and reverse-bias p-n junction diode.
APPARATUS: Junction diode [BY 126, OA 81 etc.], and a diode board.
FORMULA:
Forward resistance:
∆𝑽𝒇
𝑹= Ω
∆𝑰𝒇
where ∆𝑉𝑓 is the change in forward voltage (V)and ∆𝐼𝑓 is the change in forward current (A)

PROCEDURE:
1. Connect the circuit as shown in the forward bias mode i,e n-type to negative and p-type to
positive.
2. Increase the voltage and identify the corresponding current in the Ammeter.
3. Repeat the experiment for different values if V
4. Connect the Diode in the reverse bias mode. i,e n-type to positive and p-type to negative.
Repeat the experiment.
5. Plot the graph and determine the required resistance.
PRECAUTIONS:
1. The connections should be tight.
2. The voltage should be as low as possible.
3. Do not allow the current to pass through the diode for a long time.
4. Forward-bias voltage beyond breakdown should not be applied.
5. Reverse-bias voltage beyond breakdown should not be applied.
SOURCES OF ERROR:
1. The junction diode supplied may be faulty.
2. The ammeter and voltmeter may not connected with proper polarity.
RESULT:
1. The forward bias and reverse bias characteristics curve for PN junction diode are studied.
2. The forward resistance =________Ω

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