Light: Reflection and Refraction

Light Reflection and Refraction

• Light allows sight by originating from a source, reflecting off a surface, entering the eyes, and being processed by the brain.
• James Clerk Maxwell proposed light is electromagnetic radiation, based on electric and magnetic waves traveling at light speed.
• Light possesses a dual nature, acting as both a wave and a particle.
• As a wave, light bends around obstacles; as a particle, it reflects or passes through barriers.
• Wave properties are demonstrated through diffraction, interference, and polarization.
• Diffraction occurs when light waves bend around barriers.
• Interference results from overlapping waves that either reinforce or cancel each other.
• Polarization is when unpolarized light reflects off a surface, causing it to travel linearly or circularly.
• The photoelectric effect demonstrates light's particle nature, where photons release photoelectrons upon collision with electrons.
• Light can be absorbed, reflected, refracted, or transmitted when moving between media.
  • Absorption involves the medium absorbing the light.
  • Reflection involves the light bouncing off the medium's surface.
  • Refraction involves the light bending as it passes through the medium.
  • Transmission involves the light passing through the medium unchanged.
• Light reflecting off a plane mirror experiences minimal absorption.
• Light's characteristics include speed (c), the product of wavelength and frequency, and its constant value of about 3 x 10^8 m/s.
• Fermat's principle explains light's behavior through the principle of least time, rectilinear propagation, and the law of reflection.
• Principle of Least Time: Light takes the quickest path between two points.
• Rectilinear Propagation: Light travels in straight lines through homogenous media.
• Law of Reflection: Incident ray, normal, and reflected ray are coplanar; incidence angle equals reflection angle.
• Mirages illustrate Fermat's principle through sunlight bending between air temperature layers.
• Plane mirrors possess regular surfaces that reflect light in one direction.
• Plane mirrors create virtual, erect images behind the mirror where object distance equals image distance.
• Image qualities are determined by whether it's real or virtual, inverted or erect, and its magnification.
  • Real images form via actual light ray intersection.
  • Virtual images are apparent images formed by extended lines.
  • Inverted images appear upside down.
  • Erect images appear with the same orientation.
• The principle of reversibility of light states that light retraces its path if it falls onto a surface.
• Spherical mirrors are polished, reflective curved surfaces from hollow spheres.
  • Spherical mirrors include concave and convex types.
• Concave mirrors feature inner reflective surfaces.
• Convex mirrors feature outer reflective surfaces.
• Spherical mirror terms:
  • Pole: Midpoint of the spherical mirror (P).
  • Center of Curvature: Sphere's center (C).
  • Radius of Curvature: Distance from C to P (R).
  • Principal Axis: Line through P and C.
  • Focus: Point where parallel rays converge (F).
  • Focal Length: Distance from P to F (f = R/2).
• Ray diagram rules:
  • A ray parallel to the principal axis reflects through the focus.
  • A ray through the focus reflects parallel to the principal axis.
  • A ray through the center of curvature reflects back along the same path.
• Concave mirror image formation depends on object position:
  • At infinity: Image at focus, point size, real, inverted.
  • Beyond C: Image between F and C, smaller, real, inverted.
  • At C: Image at C, same size, real, inverted.
  • Between C and F: Image beyond C, larger, real, inverted.
  • At F: Image at infinity, highly magnified, real, inverted.
  • Between F and Pole: Image behind mirror, larger, virtual, erect.
• Convex mirror image formation:
  • Between pole and infinity: Image behind mirror, between pole and focus, virtual, erect.
  • At infinity: Image behind mirror, at focus, virtual, erect.
• Concave mirrors are in dental mirrors, solar cookers, and headlights.
• Convex mirrors are in hospital corridors, car rearview mirrors, and intersections.
• The mirror formula: 1/f = 1/u + 1/v.
• Magnification: m = image height / object height.
• Ray diagram sign conventions:
  • Distances along incident light are positive.
  • Distances against incident light are negative.
  • Heights above the principal axis are positive.
  • Heights below the principal axis are negative.
• Negative magnification equals real image; positive equals virtual.
• Refraction is the bending of light passing through different media.
• Laws of Refraction:
  • Incident ray, normal, and refracted ray lie in the same plane.
  • Snell's Law: sin i / sin r = constant.
• Light through glass slabs emerges parallel but displaced.
• Light bends toward the normal going from rarer to denser media, and vice versa.
• Refractive index (n) determines the degree of bending.
• Refractive index: n = sin i / sin r.
• Refractive index types:
  • Relative: ratio of refractive indices of two media.
  • Absolute: ratio of refractive index of a medium to vacuum.
• Total internal reflection occurs when light from a denser medium strikes at an angle greater than the critical angle.
• Spherical lenses refract light due to curvature.
  • Convex lenses converge light.
  • Concave lenses diverge light.
• Lens terms:
  • Pole (optical center): Lens center (P).
  • Principal axis: Line through optical center and curvature center.
  • Paraxial rays: Rays near and parallel to the principal axis.
  • Center of curvature (C): Center of the sphere making up the lens.
  • Focus (F): Convergence or divergence point.
  • Focal length (f): Optical center to focus distance.
• Lens ray diagram rules:
  • A ray parallel to the principal axis passes through the focus.
  • A ray through the optical center goes straight.
• Convex lens image formation varies:
  • At 2F1: Image at 2F2, same size, real, inverted.
  • Between F1 and 2F1: Image beyond 2F2, larger, real, inverted.
  • Beyond 2F1: Image between F2 and 2F2, smaller, real, inverted.
  • At F1: Image at infinity, highly magnified, real, inverted.
  • Between F1 and optical center: Image on the same side, larger, virtual, erect.
• Concave lens image formation:
  • At infinity: Image at focus, virtual, erect, diminished.
  • Between infinity and optical center: Image between focus and optical center, virtual, erect, diminished.
• Convex lenses are in microscopes, cameras, projectors, telescopes, and magnifying glasses.
• Concave lenses are in binoculars, telescopes, eyeglasses, and flashlights.
• Lens sign conventions:
  • All distances from the optical center.
  • Distances with incident rays are positive, against are negative.
  • Heights above are positive, below are negative.
• Object distance (u) is negative if the object is in front of the lens.
• Object distance (u) is positive and a virtual project if behind the lens.
• Concave lenses have negative focal lengths.
• Convex lenses have positive focal lengths.
• The lens formula: 1/v - 1/u = 1/f.
• Magnification: m = image height / object height = v/u.
• Negative magnification = real, inverted image.
• Positive magnification = erect, virtual image.
• Power of a lens: P = 1/f in diopters.
• A diopter measures refractive power.

The Human Eye and The Colorful World

• Eyes enable sight and perception.
• Human eyes function like cameras, composed of blood cells and tissues.
• Eyes offer a 180-degree view and 3D vision.
• They aid in perceiving object depth and distance.
• Each eye captures separate images combined by the brain.
• Eye gaps capture images from different angles.
• The retina is the back surface where images form.
• Real and inverted images are formed
• It contains rods and cones that help with light intensity and color differentiation, respectively.
  • Rods respond to brightness.
  • Cones differentiate colors
• Cornea: A transparent layer protects the eyes and refracts light.
• Aqueous humor: Fluid between the cornea and lens.
• Eye lens: A convex lens of jelly adjusts focal length using ciliary muscles.
• Vitreous humor: Fluid between the lens and retina.
• Ciliary muscles: Change eye lens shape and focal length.
• Pupil: Adjustable opening controlling light intensity.
• Iris: Colored part controlling pupil size and light reaching the retina.
• Optic nerve: Transmits visual information to the brain.
• Blind spot: Optic nerve junction without rods or cones.
• Eyeballs are spherical, about 2.3 cm in diameter.

How Eyes Works?

• Light enters the eye through the refracted cornea.
• Light passes through the pupil, and intensity is controlled by the iris.
• Light goes through the lens to form the image on the retina.
• The photoreceptors convert light into electrical signals, which are then processed by the brain.

Pupil

• Iris functions like entering a cinema hall.
• Iris contracts in bright light, decreasing light entering the eye.
• Iris expands in dim light, increasing light entering the eye.

Persistence of Vision

• Brain merges successive images into one moving image.
• The brain retains images for 1/16th of a second.
• Film makers take of movie using the vision.

Power of Accommodation

• Ciliary muscles adjust the focal length of the eye lens.
• Relaxed ciliary muscles result in a thin lens for remote vision.
• Contracted ciliary muscles result in a thick lens for nearby vision.
• Near point for distinct vision is 25 cm.
• Normal point is infinity.
• Color blindness is genetic.
  • Types: monochromacy and dichromacy.
  • Three cone types: red, blue, and green (RGB).
  • Total color blindness involves two or more absent cones.
  • Partial color blindness, or dichromacy, involves one cone being absent.

Defects of Human Eyes

• Four types of defects: myopia, hypermetropia, astigmatism, and presbyopia.

Myopia

• Near objects are seen clearly, far objects are not.
• Light forms in front of the retina.
• Reasons include elongated eyeballs and increased lens power.
• Concave lenses are used for correction.

Hypermetropia (Far-Sightedness)

• Far objects are seen clearly, near objects are not.
• Normal vision focuses on the retina at 2.5 cm.
• Images form beyond the retina.
• Convex lenses are used for correction.

Presbyopia

• Caused by the old age
• Near and non-near objects cannot be seen completely.
• Concave or Convex lenses can be used.
• Bifocal lenses are used to have both concave and convex in one lens.

Astigmatism

• Vision is blurry in all directions.

• Cylindrical lenses are used.

• D-format lenses are used.

• Cataracts involve a hazy lens corrected by surgery.

Eye Donation

• Corneas and other eye tissue donated to treat corneal blindness or blood infection
• Eyes can be donated post-death.

Refraction Through a Prism

• No parallel of emergent light in rectangle; however prism does have parallel emergent light.

Prism

• Triangular prism has:
  • 3 Triangular bases
  • 3 Rectangular sides

Important Angles

• Angle of the Prism is formed by two surfaces angles.
• Angle of Deviation is due to the incident light extending the angle.
• Angle of incidence = 1
• The angler = R

The angle of emergence = E

Dispersion of White Light

• "VIBGYOR" colors are formed by the prism: violet, indigo, blue, green, yellow, orange, and red. _organized =the sequence colour. is visibles of.
• Angle deviation varies by color and the refractive index

Issac Newton's Experiment

• Spectrum first observed by Newton with sunlight.
• Observation of while Light is 40% is seven colours.

The Red -combiant to the Light, to the convert is while

Rainbow

• Spectrum caused by light refracting through water droplets. -Is prsim
• Dispersion causes the Rainbow. -Reason of Disperson is the Rebbion
• Water droplet interference & refraction cause seven colors. Total internal reflection forms rainbow. Always forms opposite side of the sunlight. .The process of light inters of & refracts cause & color. Red is on top; violet is on the bottom.

The rebbin has 3 Processes

B -Distraction of refraction

C -refraction internal

D -refractions

Atmospheric Refraction

Multiple refractions lights occur due to varying air density layers. Reflective indecies of Atmosphere refraction

Why stars twinkle. Because- Star Path- Change & Density Change to Time

• Actual sunrise 2 minutes early.

• Actual sunset 2 minutes late. Refracture the Null Artificial start postion due to more and more layer. Bends - Because stars are point sources, refraction cannot be nulled out

• Planets do not tinkle. Sunrise occurs 2 mins early. Sunset occurs 2 minutes late. -4minutes

• Suns - Refraction occurs, The sun appear Flatten disk. The original of Sun

Effects that involves :

• Scattering of light in atmosphere by dust and molecules.

Reyghle = -1 Small a

• Amount of scatting = 1/ power of wavelength Light scalteri

Releigh scattering is the blue in sky. Small particles scatter blue. Large Particle Is Whites

Density.incidences & frequncies.The tinale of that one

• *Forets Beames & by Tinadle Effects Red is signal color, scatters, so visible to avoid accidents. At 12 PM, sun light is recombinants and whilests.

Electric Current and its Effects

• Electric current flows through a wire, analogous to water flowing in a river.

• Is flows from different direction to another conducter.

• Electric current is the rate of electric charge.

• Electric Potential(Voltage) cause a elecrtial flow in Electric Circuits

• Electric Charge of flow close or continuious

• Ammeter measures current (A). Formula: I=Q/T.

• I=1C/T

• *A = Charges /Second (Electric Chargers

• Electric Potential = (V)- amout of pint chargers -V=w/00

• Electric Potentias (Volts)

• *Volts -Allexandra of Volt,

• **-Electrical step

• *H=V - -

• _ohum Lowes

Ohm's Law

• • V=IR Ohm means 1voltiues from to 1- ampess current. -is
• *Resistenc= =stop_ Good- metals
• *-The increase length Incerese- the length of resistance +
• • Increase Area -Decreased the + Reduction
• *formula- p= r= pL/a (p) is constant p= OHUM (p)metres

Metals or

• Glasses is insturacturac
• Reissttances* changes Tempeture. The Temp changes - The Resistnace

Combination Register

Series resistence. Head

paralied -Same viriates

series R=++. + Paralied = THE HEATING IF A LIGHT FORMALE = OHUM

Heat Formula

• *H=iRT , CONDUCT=Current" __Reductions = Resistnace
• *T= Times flow
• *Heat of wire comes from Tungstens and Nitrogen
• The elecritous curenrts & Heat is Easy
• FUSE used for safely , avoid voltags
• Made of All metals
• Earrthing safe the save & Power is elecrtius power, works, with time and energy =p=W/time of Takeys =1 waTTs if 1 joul

ELITRIC safety for save.