m.s.gayathri, lecturer physicskea.kar.nic.in/vikasana/physics_puc/e1_ppt.pdf8. define power of a...

TOPIC 1 2 4 5 mark 5 markTOPIC 1 mark

2 mark

4 mark

5 mark theory

5 mark problem

Geometrical O i

1 1 1 1 COptics

Physical Optics 3 3 1 PC 1

El i 1 2 1 T/P 1 CElectrostastics 1 2 1 T/P 1 C

Current Electricity

2 4 1 T/P 2 1 C

TOTAL 10 14 4 8 4

Atomic Physics 3 4 1 T/P 4 1 C


Laws of refraction

n sin i = n sin r

Laws of refraction

n1 sin i = n2 sin r


LATERAL SHIFTLATERAL SHIFT

When a ray of light is incident obliquely on a parallel sided glass slab the emergent ray shifts laterally . The perpendicular distance between the direction of distance between the direction of the incident ray and emergent ray is called “lateral shift’’.is called lateral shift .


N`P

Ai

BA

r i-r

B

T tQ

r

D CN

T

R

t

D CN

S

R


ABCD=Principal section of a glass slabof a glass slab

PQ = incident ray QR = refracted rayRS = t RS = emergent ray NN`= normalRT = lateral shiftBC = t = thickness of

the slabi = angle of incidencei angle of incidencer = angle of refraction


Consider ▲NQR,cos r = QNQR

QR=QNcos r

From the ▲QRT,sin(i-r)= RTQR

RT cos rQN


NORMAL SHIFTNORMAL SHIFTThe apparent shift in the position of an

bj t l d i di d i d

N`

object placed in one medium and viewed along the normal, from the other medium.

SN

N PQ

r

S

rN

It R

Pi

r

it R

O© M.S.GAYATHRI, Lecturer in Physics

O

OP = incident rayPQ = refracted ray produced

backwards meet ON at Ibackwards meet ON at INN`= normalOI = normal shiftRPO = i = angle of incidence = NPORPO = i = angle of incidence = NPOQPS = r = angle of refraction = NIPt = thickness of the optical medium

From the ▲ NPO

From the ▲ NPI


n1 sin i = n2 sin r

H 1 Here n1 = n n2 = 1

P i i t hi h P is a point which very close to N


TOTAL INTERNAL REFLECTION

i Ci>C

r 900

i C

denser medium


AREFRACTION THROUGH A PRISM

AZ

i1 i1r1 r2

d RM

Qr1 r2

SNP

B C


ABC = principal section of the prism

BC = BaseBC = BaseA = Angle of the prismPQ = Incident rayyQR = Refracted rayRS = Emergent rayZMS = d = Angle of deviationZMS = d = Angle of deviationi1 = Angle of incidencer1 = Angle of refraction1 gr2 = Angle of incidence at the

face ACi = Angle of emergence


i2 = Angle of emergence

Consider the Quadrilateral AQNRIn the ∆QNR

A QNR 1800A + QNR = 1800

r1 + r2 + QNR = 1800

ti th b t ti hequating the above two equations, we haveA + QNR = r1 + r2 + QNR

A = r1 + r2 ---------------------(1)A = r1 + r2 ---------------------(1)

d = (i1 – r1) + (i2 – r2) d = (i1 + i2) – (r1 + r2) = i1 + i2 - A (from 1)d + A = i1 + i2 ---------------------(2)


ddat minimum deviationi1 = i2 = i

D

1 2r1 = r2 = rd = D d

(1) A = 2r or r = A/2

Di ii1 i2

(1) A = 2r or r = A/2(2) D + A = 2i or i = (A+D)/2


REFRACTION THROUGH REFRACTION THROUGH CURVED SURFACES

Curved surface: It is a part of a sphere.

Principal axis: The horizontal line passing through the centre of the curved surface.

Pole(P): Centre of the curved surface.

Centre of curvature(C): It is a point on the principal axis which is the centre of the sphere in which curved surface is a part


sphere in which curved surface is a part.

Principal focus(F): It is a point on the Principal focus(F): It is a point on the principal axis where parallel rays from infinity converge or appear to diverge from that pointconverge or appear to diverge from that point

Focal length (f): It is the distance Focal length (f): It is the distance between the principal focus and the pole.

Radius of curvature(R): It is the distance between centre of curvature and the pole


Relation between n,u,v&R

rN

Mi

r

C O I P

i

C O I P


OM = incident rayOM incident rayMN = refracted rayMI = refracted ray produced

backwardsbackwardsCP = radius of curvature (R)OP = object distance (u)IP = image distance (v)i = angle of incidencer = angle of refractionr angle of refraction


Applying sine rule to the ▲s CMO & CMI

Dividing equation (2) by equation (1)Dividing equation (2) by equation (1)


= X

==

We know that n1 sin i = n2 sin r

=


Dividing the above equation through out by uvR


M is a point which is very close to P, therefore

IM ≈ IP = -v (because imageis virtual)is virtual)

OM ≈ OP = u

CO = CP – OP = R - u

CI = CP - IP = R + v


Lens maker’s formulaA

E FE F

IB DP

O I`u v IB DO I

V`

© M.S.GAYATHRI, Lecturer in PhysicsC

OE = incident rayFI = refracted rayO = point objectI` = virtual object for the surface ADCOP = = bj t di t OP = u =object distance R1 ,R2 =radii of curvatures of the

surfaces ABC and ADCsurfaces ABC and ADCPI =v=image distanceP I` =v` =image distance for the first g

surface


For the refraction through surface ABCFor the refraction through surface ABC,

f f CFor the refraction through surface ADC,

Negative sign indicates that the object is virtual


(1) (2)Adding (1) and (2)


Two thin lenses in contactTwo thin lenses in contact

L1 L2

O I I`

u vV`V


Let us consider two thin lenses in Let us consider two thin lenses in contact let f1 and f2 be their focal lengthslet u=object distance

v =image distancev`=virtual image distance g

For refraction through first lens,

here I` is the image formed


For refraction through second lens,here I` serves as virtual object for the here I serves as virtual object for the second lens.

Adding equations (1) and (2)


let F be the effective focal length let F be the effective focal length of the combination.


Questions carrying ONE mark eachy g1. Define critical angle.

2. Mention an application of total internal 2. Mention an application of total internal reflection.

3. What is dispersion of light?

4. Write the expression for the deviation produced by a thin prism.

5. Define dispersive power of the material of a prism.

6. What is angular dispersion?

7. Write the condition for dispersion without deviation.


p

8. Define power of a lens.

9. What is magnification?

10. Write the relation between power and focal length of a lens.

11. Write the expression for the equivalent focal l th f t thi l t d b di t length of two thin lenses separated by a distance.

12. What is a thin prism?

13. What is the lateral shift produced by a parallel sided glass slab for grazing incidence of light?

14. A thin convex lens of focal length 0.1m & a thin concave lens of focal length 0.1m are placed co-axially in contact. What is the net power of the


y pcombination?

Questions carrying two marksy g1.Mention the conditions for total internal

reflection to occur.•the light ray should travel from denser medium to rarer the light ray should travel from denser medium to rarer medium•the angle of incidence must be greater than critical angle

2.Arrive at the relation between critical angle and refractive index.

c

Here n1=n, i=c, n2=1 & r=900

n sinc=1 sin 900

n sinc 1n sinc=1

n=


n

3.Write the ray diagram showing the experimental arrangement for pure spectrum.

S

L1L2

R

V

P


4.What is an optical fibre? on what principle does it work?

An optical fibre is a thin transparent fibre which transmits light along any desired path. It works on the princple of TIR.

5.What is a pure spectrum? give an example.If the constituent colours are seen distinctly in a

6 What is an impure spectrum? give an example

spectrum, it is called pure spectrum.Example: Spectrum produced in the laboratory

6.What is an impure spectrum? give an example.

A spectrum in which the constituent colours overlap and are not seen distinctly is called impure spectrum.Example: Rainbow


Example: Rainbow

7.Calculate the refractive index of a pair of media given critical angle as 40˚.g ggiven C=40˚ ,n=1

8 Calculate the angle of deviation produced by a 8.Calculate the angle of deviation produced by a thin prism of refracting angle5˚ and refractive index 1.5.

d=?,A=5˚,n=1.5 d=(n-1)A=(1.5-1)X5˚=0.5X5˚=2.5˚


9.An object is kept at a distance of 0.12m from a convex lens forms an image at a distance of 0.18m.calculate the magnification produced.

u=0.12m,v=0.18m, m=?


10 Two thin convex lenses of focal10.Two thin convex lenses of focallengths 0.15m & 0.2m are separated bya distance of 0.6m. Find the effectivefocal length of the combination.

given:f1=0.15,f2=0.2,d=0.06,F=?


Question carrying FIVE mark each

1. What is lateral shift? Derive an expression forlateral shift produced by a parallel sided glassslab for oblique incidenceslab for oblique incidence.

2. What is normal shift? Derive the expression forl hift d d h bj t inormal shift produced when an object in a

denser medium is viewed normally through air.

3 D i th i f f ti i d i3. Derive the expression for refractive index interms of the angle of the prism and angle ofminimum deviation.


4.Derive the relation connecting n,u,v & R forrefraction at a spherical surface concavetowards a point object in a densertowards a point object in a densermedium.

5.Derive lens maker’s formula.

6.Derive the expression for the effectivefocal length of two thin lenses ingcontact.


•Read the given problem twice

W it th i d t•Write the given data•Write a relevant formula/e connecting the given data

•Substitute and simplify

•Write the result with S.I unit


List of formulaeList of formulae


March 2010 : Find the real position of an air bubble in a glass cube of side 0.3 m if the bubble appears to be at a distance of 0.05 m from one face and at 0.15 m from the opposite face.

Solution:Here apparent distance from both the faces are given. A D = 0 05 mA.D1 = 0.05 mA.D2 = 0.15 m

Let ‘x’ be the real distance from the first face.Real distance from the opposite face is


pp(0.3-x) m

We know that

Therefore the real position of the airTherefore the real position of the airbubble in the glass cube is 0.1 m fromthe first face or 0.2 m from theopposite face


opposite face.

March 2008: Focal length of convex lens is March 2008: Focal length of convex lens is 0.1 m. A liquid lens is formed between a plane surface and one face of this lens of radius of surface and one face of this lens of radius of curvature 0.12m. The converging combination formed is found to have a focal length 0.18 m. gCalculate the refractive index of liquid.Solution:

Given F=0.18 m, f1 = 0.1m, R1=0.12m, n=?


Here radius of curvature of the plane surface is infinity is infinity


March 2011: A concave lens when placed in air has a focal length of 0.4 m and has a refractive index of 3/2. What will be its focal length when immersed in water of refractive index 4/3.Solution:

Given: f=0.4 m, n of glass=3/2, f of lens when immersed in water=? R.I of water 4/3


Simplify and arrive at


March 2006: A small air bubble is found 0.04 m inside the glass sphere of refractive 0.04 m inside the glass sphere of refractive index 1.5 When viewed normally from outside it is seen at a depth of 0.03 m. Calculate the radius of curvature of the glass sphere.Solution:

Given u=0.04m, n=1.5, v=0.03m, R?


R=0.119m


m.s.gayathri, lecturer physicskea.kar.nic.in/vikasana/physics_puc/e1_ppt.pdf8. define power of a...

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