EsroMagican

 

                           LIGHT

·      WHAT IS LIGHT?

·      HISTORY OF LIGHT

·      SPEED OF LIGHT AND ITS HISTORY

·      REFLECTION

·      ANGLES IN A REFLECTION

·       DIFFERENT TYPES OF REFLECTION and LAWS OF REFLECTION

·       PLANE MIRRORS

·      CONCAVE AND CONVEX MIRROR

·       rules for making RAY DIAGRAMS

·      RAY DIAGRAMS OF CONVEX AND CONCAVE MIRRORS

·      cartesian sign convection

·      MIRROR FOMULA AND ITS DERIVATION

·      APPLICATIONS OF MIRRORS

·      REFRACTION and LAWS OF REFRACTION

·       LENSES­­­­­­--CONVEX AND CONCAVE LENSES

·      APPLICATIONS OF LENSES

·      DISPERSION OF LIGHT

·      PRISM

·      APPLICATIONS OF DISPERSION OF LIGHT

·      POLARIZATION OF LIGHT

·      APPLICATIONS OF POLARIZATION OF LIGHT

·      conclusion

WHAT IS LIGHT?

LIGHT IS A FORM OF ENERGY THAT CAUSES SENSATION OF VISION.LIGHT IS THE ELECTROMAGNETIC FORCES THAT CAN BE PERCIEVED BY HUMAN EYE.IN PHYSICS,IT REFERS TO ELECTROMAGNETIC RADIATION OF ANY WAVELENGTH

It can be described as both a wave and a particle (photons) and is a form of energy. Light exhibits properties like reflection, refraction, and absorption when interacting with different materials. It also plays a crucial role in photosynthesis

Sources of light includes:

natural sources

man made sources

 

HISTORY OF LIGHT

The history of light spans millennia, evolving from early observations of natural phenomena to complex scientific theories. Early understandings viewed light as emanating from sources like the sun or even the human eye. Ancient Greeks, Egyptians, and others contributed ideas about light's nature and behavior. Later, significant breakthroughs came from Islamic scholars like Ibn al-Haytham, who revolutionized the understanding of vision. The particle theory proposed by Isaac Newton, leading to the eventual understanding that light exhibits both wave-like and particle-like properties.

 The CMB is the oldest light in our Universe; it was emitted almost 14 billion years ago, just 400,000 years after the Big Bang (when the Universe was only 0.003% of its current age). 

SPEED OF LIGHT AND ITS HISTORY

Speed of Light in a vacuum is 3*10^8(or)299,782,458m\s

The first measurement of the speed of light was achieved by Ole Rømer in 1676 by observing the eclipses of Jupiter's moon Io. Rømer noticed that the timing of these eclipses varied depending on the Earth's position relative to Jupiter, concluding that it took time for light to travel these varying distances. While not initially precise, his work provided the first evidence that light travels at a finite speed and not instantaneously. 

Here's a more detailed look at the history:

·       Ancient Ideas:

Early thinkers like Empedocles proposed that light had a finite speed, while others believed it was instantaneous. 

·       Galileo's Attempt:

Galileo attempted to measure the speed of light by observing the time it took for light to travel between two distant locations using lanterns, but his experiment was unsuccessful due to the limitations of human reaction time. 

·       Rømer's Discovery:

Ole Rømer, a Danish astronomer, used the eclipses of Jupiter's moon Io to make the first successful measurement. He observed that the eclipses appeared to occur earlier when the Earth was closer to Jupiter and later when the Earth was farther away. 

·       Rømer's Calculation:

Rømer correctly interpreted this variation as evidence that light takes time to travel. He estimated that light took about 22 minutes to cross the diameter of the Earth's orbit. 

·       Huygens' Refinement:

Christiaan Huygens used Rømer's estimate and knowledge of the Earth's orbital diameter to calculate a speed of light of 220,000 km/s, which was a significant improvement over previous ideas. 

·       Fizeau's Measurement:

In 1849, Hippolyte Fizeau used a rotating toothed wheel and a mirror to make the first successful terrestrial measurement of the speed of light, obtaining a value of 315,000 km/s. 

·       Foucault's Refinement:

Léon Foucault further refined Fizeau's method using a rotating mirror and achieved a more accurate value of 298,000 km/s. 

REFLECTION OF LIGHT

THE phenomenon due which a beam of light travelling through a certain medium , on striking a smooth polished surface bounces of from from it in some other direction is called reflection of light .

incident ray :a light ray from a source of light reaching a reflecting surface is called incident ray

reflected ray:a light ray that bounces from the reflecting surface and travels in the sae optical medium is called reflected ray

angles in a reflection

normal: the perpendicular to the reflecting surface drawn at the point of incidence is called normal

angle of incidence:the angle between normal and incident ray is called angle of incidence

angle of reflection:the anglr between normal and reflected ray is called angle of reflection

angle of deviation: the angle at which the incident ray deviates from its path due to presence of mirror is called angle of deviation

glancing angle of incidence: the angle that incident ray makes with the mirror is called glancing angle of incidence

glancing angle of reflection: the angle between the reflected ray is called glancing angle of reflection

different types of reflection and laws of reflection

 

different types of reflection

Regular reflection	Irregular reflection
When a parallel beam of light on striking some smooth and polished surface is reflected back as a parallel beam of light is called regular reflection	When a parallel beam of light on striking a rough surface is reflected in different directions is called irregular reflection

 

laws of reflection

A.       the incident ray , reflected ray, normal all lie in the same plan

B.       the angle of incidence is always equal to angle of reflection

plane mirrors

 A plane mirror is a flat, smooth mirror that reflects light at the same angle it hits the surface, producing a virtual, upright, and laterally inverted image that is the same size as the object

charecteristics of image formed in plane mirror

·      image is virtual

·      image is erect

·      image is of the same size as the object

·      image is formed as far as behind the mirror, as the objectis in front of it

·      image is laterally inverted

Plane mirrors have various applications, including:

·       Everyday Use: Used in dressing mirrors, rearview mirrors, and other common applications where a reflection is needed. 

·       Solar Cookers: Plane mirrors can reflect sunlight onto a focal point to heat food. 

·       Periscopes: Used in periscopes to allow observation from a hidden position. 

·       Optical Instruments: Used in some optical instruments and scientific experiments. 

concave and convex mirrors

Concave mirror	Convex mirror
A mirror which is polished from bulging side of hollow sphere , such that the reflecting surface is towards hollow side of mirror	A mirror which is polished from hollow side of sphere , such that the reflecting surface is towards bulging side of mirror

 

terms related to spherical  mirrors

pole	The midpoint of a spherical mirror is called pole
Centre of curvature	The centre of sphere , of which the sperical mirror is a part is called as centre of curvature
Principal axis	An imaginary line passing through pole and centre of curvature of a spherical of aaspherical mirror is called principal focus
Linear aperture	The diameter of a spherical mirror is called linear aperture
Principal focus	`it is a point on principal axis , where a beam of light parallel to principal axis, after reflection , either actually meets or appears to meet.
Focal length	The linear distance between the pole and the principal focus is called focal length
Radius of curvature	The linear distance between the pole and centre of curvature is called radius of curvature

 

 

RAY DIAGRAMS

 

concave  mirror

rule1:a ray of light which is parallel to the principal axis of a concave  mirror, passes through its focus after reflection from the mirror

rule2: a ray of light passing through the centre of curvature of concave mirror is reflected back along the same path

rule3: a ray of light passing through he focus of a concave mirror becomes para llel to principal axis after reflection

rule4: a ray of light which is incident at pole of a concave mirror is reflected back making the same angle with the principal axis

 

convex mirror

rule1:a ray of light which is parallel to the principal axis of a convex  mirror, appears to be coming from its focus after reflection from the mirror

rule2: a ray of light going towards the centre of curvature of convex mirror is reflected back along the same path

rule3: a ray of light going towards   the focus of a convex mirror becomes parallel to principal axis after reflection

rule4: a ray of light which is incident at pole of a concvex mirror is reflected back making the same angle with the principal axis

 

 ray diagrams of concave and convex mirror

 convex

concave

 

 cartesian sign convention

1)  all distances parallel to the principal axis are measured from pole of spherical mirror.

2)  the distances measured in direction of incident light are taken as positive

3)  the distances measured in direction opposite to direction of incident light are taken as negative

4)  the height of objects measured upwards and perpendicular to the principal axis are negative

5)  the heights  of the objects measured downwards and perpendicular to principal axis are considered as negative

mirror formula and its derivation

The mirror formula, expressed as 1/v + 1/u = 1/f, establishes a relationship between the image distance (v), object distance (u), and focal length (f) of a spherical mirror. It's a fundamental equation in optics, applicable to both concave and convex mirrors, though sign conventions differ. The derivation involves geometric principles and similar triangles formed by light rays reflecting off the mirror. 

Derivation of the Mirror Formula:

1. 1. Diagram:

Consider a concave mirror with an object placed at a distance 'u' from the pole (center of the mirror). An image is formed at a distance 'v' from the pole. The focal length is 'f'. 

2. 2. Similar Triangles:

·       Identify two sets of similar triangles in the diagram. One pair is formed by the object and image heights (h and h') with the object and image distances (u and v). 

·       Another pair of triangles is formed by the focal length (f) and the height (h) of the object, and the distance from the focal point to the image. 

3. Applying Similarity Ratios:

Using the properties of similar triangles, we can set up ratios:

·       h'/h = -v/u (where h' is the image height, and the negative sign indicates an inverted image). 

·       h'/h = -(v-f)/f. 

4. Equating and Rearranging:

·       Equate the two expressions for h'/h: -v/u = -(v-f)/f. 

·       Simplify and rearrange the equation to get: v/u = (v-f)/f. 

·       Further simplification leads to: v/u = v/f - 1. 

·       Dividing both sides by v: 1/u = 1/f - 1/v. 

·       Finally, rearranging to the standard form: 1/v + 1/u = 1/f. 

Key Points:

·       The derivation relies on the laws of reflection and the properties of similar triangles. 

·       The sign conventions are crucial. 

·       This formula applies to both concave and convex mirrors, with adjustments for sign conventions. 

application of mirrors

1)  plane mirrors are used to make kaleidoscopes and reflecting periscopes

2)  they are used to provide false dimensions in some shops

3)  they are used in solar cookers for reflecting the rays of the sun into the interior of solar cooker

4)  they are used for signaling by scouts and the army personal

5)  convex mirrors are used to make side view mirror  in  vehicles

6)   they are used in atm for security

7)  concave mirrors are used to produce magnified virtual images

8)  due to its ability , it is used by e.n.t specialists to view interior portion of body

refraction of light

when light ray travels from 1transparent medium to another ,there is a deviation in path of light ray .this phenomenon is called refraction

laws of refraction

1) the incident ray, the refracted ray and normal at the point of incidence all lie in the same plane

2) for a given pair  of media and for the light of a given wavelength , ratio of sine of angle of incidence to sine of angle of refraction is constant

 

 

 

 

lenses

a lens is atransparent medium bound by 2 refracting surfaces. a lens can be bounded by 2 curved surfaces

convex lens

A convex lens, also known as a converging lens, is a lens that is thicker in the middle and thinner at the edges. It has the property of bending (refracting) light rays towards a focal point, causing them to converge. 

Key Characteristics:

·       Shape: Thicker in the middle, thinner at the edges. 

·       Function: Converges light rays, bringing them together at a focal point. 

concave lens

A concave lens, also known as a diverging lens, is a lens that is thinner in the middle than at the edges. It causes parallel light rays to spread out (diverge) after passing through it. This contrasts with a convex lens, which converges light rays. Concave lenses are commonly used to correct nearsightedness (myopia) and in various optical instruments. 

Key characteristics of a concave lens: 

·       Shape: Thinner in the middle, thicker at the edges.

·       Light behavior: Diverges parallel light rays.

 

applications of lenses

convex

1. Vision Correction: 

·       Convex lenses are used in eyeglasses and contact lenses to correct hypermetropia (farsightedness), where the eye cannot focus on nearby objects. They help to converge light rays before they enter the eye, so the image is focused correctly on the retina.

2. Magnification:

·       Magnifying glasses:

Convex lenses are used to magnify objects, making them appear larger and clearer. 

·       Microscopes:

Convex lenses are crucial components in microscopes, allowing for the observation of very small objects by producing magnified images. 

·       Projectors:

Convex lenses are used in projectors to focus and magnify images from slides or films onto a screen. 

·       Telescopes:

Convex lenses (objective lens) are used to gather light from distant objects and create an image that can be further magnified. 

3. Cameras: 

·       Convex lenses are used in cameras to focus light rays onto the camera sensor or film, creating a sharp, real image.

4. Other Applications:

·       Peep holes: Convex lenses are used in peepholes on doors to provide a magnified view of the outside. 

·       Spotlights and flashlights: Convex lenses can focus light into a concentrated beam. 

·       Astronomical observations: Telescopes, which use convex lenses, are essential for observing celestial objects. 

concave

·       Binoculars:

Concave lenses help to correct image distortions and spread light evenly for a clearer view. 

·        

Peepholes:

They allow for a wider field of view through a small opening in a door. 

·       Correcting Nearsightedness:

Concave lenses help people with myopia see distant objects clearly by diverging light rays away from the retina. 

·       Flashlights:

Concave lenses can be used to spread the light beam from a flashlight, creating a wider area of illumination. 

·       Telescopes:

Concave lenses can be used in combination with convex lenses in certain types of telescopes (e.g., Galilean telescopes) to create an upright image. 

 

dispersion of light

Dispersion of light is the phenomenon where white light separates into its constituent colors (like in a rainbow) when passing through a medium like a prism or water droplet. This occurs because different colors of light travel at slightly different speeds within the medium, causing them to refract (bend) at different angles. 

 

 

 

 

 

 

prism

prism, in optics, a piece of glass or other transparent material cut with precise angles and plane faces, useful for analyzing and reflecting light. An ordinary triangular prism can separate white light into its constituent colours, called a spectrum.

geometricaly it is  a five-sided polyhedron with a triangular cross-section. In a prism, there are two identical parallel triangles opposite to each other. Along with the triangles, three rectangular surfaces are inclined to each other

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

applicat

applications of dispersion

1. Natural Phenomena:

·       Rainbows:

The most well-known example, rainbows are formed when sunlight passes through raindrops, and the light is refracted and dispersed, separating into the colors of the spectrum. 

·       Petroleum on Water:

The iridescent colors seen on spilled oil are also due to dispersion as light interacts with the thin film of oil on the water surface. 

·       Soap Bubbles:

Similarly, the shimmering colors in soap bubbles are a result of light dispersion within the thin film of soap. 

·       Diamonds:

The sparkle of a diamond is enhanced by the dispersion of light within the stone. 

 

2. Optical Instruments:

·       Prisms:

Prisms are used to separate white light into its constituent colors, enabling analysis of light sources. 

·       Spectrometers:

These instruments use prisms or diffraction gratings to analyze the spectral composition of light, helping identify the chemical makeup of materials. 

·       Microscopes and Telescopes:

While dispersion can cause chromatic aberration (color fringing), careful lens design and the use of optical coatings can minimize this effect and improve image clarity. 

·       Refractometers:

These devices use the change in refractive index with wavelength (dispersion) to measure the refractive index of liquids. 

 

3. Other Applications:

·       Telecommunications:

Dispersion in optical fibers can distort signals, but understanding and managing it is crucial for maintaining signal quality in fiber optic communication systems. 

·       Gemology:

Gemstones exhibit different colors due to the dispersion of light, and understanding this phenomenon helps in identifying and appreciating precious stones. 

·       Photography:

Lens designers use dispersion principles to minimize chromatic aberration and improve image quality. 

·       Medical Diagnostics:

Certain medical imaging techniques utilize dispersion to differentiate between different tissues and materials. 

·       Anti-counterfeiting:

Holograms on currency use dispersion to create complex images that are difficult to reproduce. 

·       Laser Tuning:

Tunable lasers use dispersion to emit light at specific wavelengths, useful in various applications. 

polarization of light

Polarization of light refers to the phenomenon where the oscillations of the electric field vector within a light wave are restricted to a single plane. In essence, it's about the direction in which the light wave's electric field vibrates as it travels. Unpolarized light, like sunlight, vibrates in all possible directions perpendicular to its direction of travel. Polarized light, on the other hand, vibrates in a single plane. 

 Types of Polarization: 

·       Linear Polarization: The electric field oscillates in a single plane. 

·       Circular Polarization: The electric field rotates in a circle as the wave propagates. 

·       Elliptical Polarization: A combination of linear and circular polarization, where the electric field rotates in an ellipse. 

applications of polarization of light

1. Reducing Glare: 

·       Polarizing sunglasses are designed to block horizontally polarized light, which is the type of light that causes glare from surfaces like water or roads. 

·       This reduces eye strain and improves visibility, especially in bright sunlight. 

2. Display Technology (LCDs):

·       Liquid Crystal Displays (LCDs) rely on polarized light to create images. 

·       Polarizers are used to control the light passing through the liquid crystals, which then modulate the light to form the desired image. 

3. 3D Movies:

·       In 3D movie theaters, different polarized filters are used for each eye. 

·       The polarized light is projected onto the screen, and the glasses allow each eye to see only the image intended for it, creating the illusion of depth. 

4. Other Applications:

·       Stress analysis in plastics:

Polarizing filters can reveal stress patterns in transparent materials like plastics, which is useful in quality control and product design. 

·       Mineral identification:

Polarizing microscopes help geologists identify minerals based on how they interact with polarized light. 

·       Astronomy:

Polarized light is used in astronomical observations to study celestial objects and phenomena. 

·       Photography:

Polarizing filters can enhance colors and reduce reflections in photographs. 

·       Communication:

Polarization plays a role in wireless communication, particularly in the transmission and reception of radio and microwave signals. 

·       Ophthalmology:

Polarized light is used in ophthalmic instruments for imaging and diagnosis of eye conditions. 

·       Chemistry:

Polarization is used in techniques like polarimetry to study the chirality of molecules. 

conclusion

light is a huge ray of knowledge ,questions and development coming on our way. let us open the windows of our mind and let the rays of wisdom enlighten us. let us uncover the history of the universe through light and its inventions.

 

thank you

 

by P.Sai likith

batch no:-0027