DISHA Concept Map

CHAPTER

01

ELECTRIC CHARGES AND FIELDS

Class XII

P2

CHAPTER

02 Class XII

ELECTROSTATIC POTENTIAL AND CAPACITANCE

P4

CHAPTER

07

GRAVITATION

Class XI

P14

CHAPTER

08

RAY OPTICS AND OPTICAL INSTRUMENTS

DISPERSION OF LIGHT The phenomenon of splitting of white light into its constituent colours on passing through a prism.

Class XII P

REFRACTION THROUGH PRISM Relation between m and dm

THIN SPHERICAL LENS Thin lens formula :

f

REFLECTION FROM PLANE SURFACE w The image formed by a plane mirror is laterally inverted. w The image formed by a plane mirror is virtual, erect w.r.t. object and of the same size as the object. w If keeping the incident ray fixed, the plane mirror is rotated through an angle q, the reflected ray turns through double the angle i.e., 2q in that direction. w Deviation suffered by a light ray incident at an angle i is given by d = (180° – 2i)

POWER OF LENSES Power of lens :

Lens maker’s formula

(Holds for any curved spherical surface)

Angular spread

O Y G B I V Screen

Mirror formula,

f

Dispersive power,

Magnification, m =

Mean deviation,

If the image is upright or erect with respect to the object then m is positive. And m is negative if the image is inverted with respect to the object.

f Laws of refraction : w The incident ray, the normal to the interface at the point of incidence and the refracted ray all lie in the same plane. w Snell’s law: (1m2 = refractive index of medium 2 w.r.t. 1)

f

100 dioptre. cm, then P = f (in cm)

SIMPLE MICROSCOPE Magnifying power For final image is formed at D (least distance), Angle subtended by the image at D b m= =a = Angle subtended by the object at infinity D For final image formed at infinity, m = f

ASTRONOMICAL TELESCOPE Magnifying power w For final image is formed at D (least distance),

f

m=

w Power: P = P1 + P2 – dP1P2 (d = small separation between the lense) w For d = 0 (lenses in contact) w Power: P = P1 + P2 + P3 + ... COMMON DEFECTS OF EYES « CORRECTING LENSES Myopia (short-sightedness)« Concave lens Hypermetropia (long-sightedness) « Convex lens Presbyopia « Bifocal lens Astigmatism « Cylindrical lens

TERRESTRIAL TELESCOPE For final image is formed at D, m

f f

For final image is formed at infinity, m

f f f

Distance between objective and eyepiece d = fo + 4f + fe

Angle subtended by the image at D

Angle subtended by the object at infinity f b –f =a f w In normal adjustment, image formed at infinity m = – fo / fe

COMBINATION OF LENSES

A terrestrial telescope Light from object at infinity

Inverted image

Upright image Erecting lenses

Objective lens

P16

TOTAL INTERNAL REFLECTION The phenomenon in which a ray of light travelling from an optically denser into an optically rarer medium at an angle of incidence greater than the critical angle for the two media is totally reflected back into the same medium. TIR conditions w Light must travel from denser to rarer. w Angle of incidence is greater than critical angle.

REFRACTION OF LIGHT

RAY OPTICS & OPTICAL INSTRUMENTS

REFLECTION OF LIGHT Laws of reflection: w The angle of incidence i equals the angle of reflection r. Ði = Ðr w Incident ray, the normal and the reflected ray lie in the same plane.

w If i < ic, then refraction takes place. w If i = ic, then grazing emergence takes place. w If i > ic, then total internal reflection takes place.

R

REFLECTION BY SPHERICAL MIRRORS

for the lens placed in air

w The SI unit of power of lens is dioptre (D). w For a convex lens, P is positive. w For a concave lens, P is negative. w When focal length (f) of lens is in

w w w w

i

Q

or d = (m – 1)A (Prism of small angle) Angular dispersion = dV – dR = (mV – mR)A

1 æ mdenser - mrarer ö æ 1 1 ö = ÷ø çè R - R ÷ø f çè mrarer 1 2

(e– r 2) d N2 e r r F 1q 2G N H

(i– r1)

E

where, dm = angle of minimum deviation A = angle of prism

REFRACTION BY SPHERICAL SURFACE Relation between object distance (u), image distance (v) and refractive index (m)

Magnification:

N1

le

ib Vis

A

Deviation of red light(dR) Deviation of R violet light (dV)

t ligh

RELATION BETWEEN m AND iC The angle of incidence in the optically denser medium for which the angle of refraction is 90°. It is denoted by ic.

Eyepiece

COMPOUND MICROSCOPE Magnifying power, m = mo × me For final image formed at D (least distance)

m=

b vo = a uo

Dö L æ çè1 + f ÷ø = f e 0

Dö æ çè1 + f ÷ø e

APPLICATIONS OF TIR w w w w w w

Fiber optics communication Medical endoscopy Periscope (Using prism) Sparkling of diamond Mirage Totally reflecting glass prisms

REFRACTIVE INDEX

Real and apparent depth

For final image formed at infinity m=

f

f Newtonian reflecting telescope

REFLECTING TELESCOPE Magnifying power When the final image is formed at D, f f m = o 1+ e fe D When the final image is formed at infinity f m= f f

(

(

Eyepiece lens Objective mirror Telescope tube

Light Diagonal mirror

CHAPTER

09

WAVE OPTICS

Class XII

P18