~CTlVITIES

~ YNO.
0
AIM
To ;dcntif.v o diode, an LED, a transistor, an IC, a resistor and a capaciJor from a mixed collection of such iJems.

APPARATUS
A mixed collection of a diode. an LED, a transistor, an IC , a resistor and capacitor.

THEORY
Diode, LED. resistor and capacitor have two legs each. A transistor has three legs. An IC bas minimum of eight legs. Most
of the IC packages have flat back. The IC and the transistor can be easily identified by counting their legs. For the
identification of diode, LED, resistor and capacitor, we can take the help of current. When d.c. is supplied to the resistor.
it sboWs constant current. When d.c. is supplied to a capacitor, a multimeter set at R shows initially a full scale deflection
which falls to uro very quickJy. Diode conducts electricity when forward biased and does not conduct when reverse
biased. When diode emits light, it is LED.

DIAGRAMS

---mrnDD- A B C
(i) Carbon resistor
D
Anode ~

(U) Electro1ytlc capaCIIOf

(iii) Junction diode

.
.
(iv) Light-emitting diode
E
m 'Q
(v)Transistor
C 1234567
(vi)IC

Q 1 2 3
(vl1)1C
4 (viii) IC chip UA741CN

1''1g. 1.01
 I ACTIVITY NO. '
b
AI M
Tr, ,, . rn 'l' diffractio11 uf li,:J,t dt1e lo ll thin slit.

APPARATUS
J. Two ordinary razor blades with sharp edges 2. A source of light J. Black paper
4. Cellotape 5. Screen.

ACTMTl£S

THEO RY
•• 7
Tht j\hl"nt~m~·rn.111 of licntling nf lighl round lhc sharp comers antl spreading into the regions of the geometrical shadow i!>
calk-\1 J1f!ra...·1ion.
1;"" J1ffraction of light waves, it is ncc~ ry that lhc llizc of the ohstaclc is comparaMe to lhc wavclcnglh or licht ln-
fact. all lhc types of wave motion cx.hihit diffraction. 'The diffraction of M)Und waves and radiowaves is U!lily observable
in daily life.
When a narrow slit is illuminated with monochromatic light. a diffractioo patte rn is obtained on the screen. 'The
diffraction pattern consists of a central maximum surrounded on either side by a number of dark and bright bands caUcd
secondary minima and maxima.

Width of ccntntl maximum = Z~).

where D is distance of screen from slit, A is wavelength of light and a is width of lhe slit.

DIAGRAM

PROCEDURE (St,pwise)
1. Take two sharp edged razor blades. Place them side by side oo a sheet of black paper. Their sharp edges should b(
dose and parallel 10 each other. Fix the blades with the help or cellotape. Cut small slit in bc1wttn the sharped~
of the blades.
2. Keep the sodium lamp 11 a distance of nearly 2 m from the blades. Switch on the sodium lamp.
3. Let the Light coming out of the slit fall on a wall or scrcon situated at a dimnce of ACarly 20 cm.
4. It will be observed thal instead of having a bright slit-like tight on the wall, the light spreads. Dark and bright bands
will be seen on the wall. This is diffraction pattern.
5. If sodium lamp is replaced by an ordinary lamp, then coloured fringes will be observed.
6. Repeat the above Sleps by increasing the width of the slit.

PRECAUTIO NS
I. Only rhe unused blades should he usc.d so lhat edges are very sharp.
2, The source of light should be kept at a distance of 2 m from the thin slit.
 7
ACTIVITIES

I ACTIVllY NO.
AI M
To in n lm s combinatio11 wiJI, thr specified / oral lc11gtl1 by usiJ.~ , lenses from the gi ~t n stl of lenses.

APPARATUS
1. A set of thin convex lenses 2. A single lens holder 3. A lens holder which can hold
4. A metre rod 5.Ascrcen. two lenses touching each other

THEORY
lf/1 and/2 are the focaJ lengths of the two lenses. then the focal length Fofthecombination of two 1en.1es is given by
.!.=...!..+...!..
F /1 /2
The reciprocal of focaJ length is called power. So, the power p of combination of two lenses is given by
P = P, + P1
where P I and P1 arc the powers of the two lenses.

PROCEDURE (Stepwise)
l. rue a convex kns. Lct/1 be its focaJ length. Pix the~ into a lens hokier.
2. Place the lens bolder on the left oftbc screen. Move the lens suitlbly to obl.ain a sharp and inverted image, of a
diswttobjcct.oothe screen.
3. Meuw-e the distance between the lens bolder and the screen· with the help of a metre rod. This distance gives the
focal length of the convex lens.
4. ReplacelhefirstleasbyalCICODdlens. uth.bethefocaJ lengthofthcsccondlens. Repwsteps2 and 3tomeuure
the focal length of the se.cond lens.
5. Now combine the rwo·lenscsoffoca] lengths Ji arvJfi. Place the combination in a lens hokier which can hold the
two lenses touehu:lg each ocher. Repeal steps 2 8M 3 to find the focal length F of lens combination.

OBSERVATIONS
1. The focal length of the first convex Jens./1 = .. ..... cm
2. The focal length of the second convex Jcns, / 2 = ........ cm
3. The focal length of the combination of two lenses of focal lengths/1 and/2 , F = ........ cm

CALCULATIONS

Focal length, F::t-£7;

Experimental value of F = ....... cm

Ill PHYSICS ,cnvmes-a...e XII

RESULT

The fcnnula F = l1J 2

is verified within the limits of experimental em:.-.

PRECAUTIONS
I. Lenses should be thin.
2. The aperture of lenses shouk:1 be same.
 To Observe Refraction & Lateral Deviation Of a Beam Of

Co
Alm
Light Incident Obliquely On a Glass Slab

To observe refraction and lateral deviation of a beam of light incident obliquely on a

glass slab.

Apparatus
Glass slab, drawing board, white paper sheet, drawing pins, office pins, protractor.

Theory
When a ray of light (PQ) incident on the face AB of glass slab, then it bends towards the
normal since refraction takes place from rarer to denser medium. The refracted ray
(QR) travel along straight line and incident on face DC of slab and bends away from the
normal since refraction takes place from denser to rarer medium. The ray (RS) out
through face DC is called emergent ray.
From the following diagram

1. The incident ray is parallel to the emergent ray i.e . i = e .

2. The emergent ray is laterally deviated from its original path (incident ray) by a
distanced= t sec r sin (i - r).

Diagram

Refraction throuab. slue alab.