Physics LIGHTS AND OPTICS description with basics.pptx.pdf

Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories on light and vision developed by ancient Greek philosophers, and the development of geometrical optics in the Greco-Roman world. The word optics is derived from the Greek term τα ὀπτικά meaning 'appearance, look'.[1] Optics was significantly reformed by the developments in the medieval Islamic world, such as the beginnings of physical and physiological optics, and then significantly advanced in early modern Europe, where diffractive optics began. These earlier studies on optics are now known as "classical optics". The term "modern optics" refers to areas of optical research that largely developed in the 20th century, such as wave optics and quantum optics.

Early history
In the fifth century BCE, Empedocles postulated that everything was composed of four elements; fire, air, earth and water. He believed that Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun. He stated that light has a finite speed.[2]

In the 4th century BC Chinese text, credited to the philosopher Mozi, it is described how light passing through a pinhole creates an inverted image in a "collecting-point" or "treasure house".[3]

In his Optics Greek mathematician Euclid observed that "things seen under a greater angle appear greater, and those under a lesser angle less, while those under equal angles appear equal". In the 36 propositions that follow, Euclid relates the apparent size of an object to its distance from the eye and investigates the apparent shapes of cylinders and cones when viewed from different angles. Pappus believed these results to be important in astronomy and included Euclid's Optics, along with his Phaenomena, in the Little Astronomy, a compendium of smaller works to be studied before the Syntaxis (Almagest) of Ptolemy.

In 55 BC, Lucretius, a Roman atomist, wrote:

For from whatsoever distances fires can throw us their light and breathe their warm heat upon our limbs, they lose nothing of the body of their flames because of the interspaces, their fire is no whit shrunken to the sight.[4]

In his Catoptrica, Hero of Alexandria showed by a geometrical method that the actual path taken by a ray of light reflected from a plane mirror is shorter than any other reflected path that might be drawn between the source and point of observation.

The Indian Buddhists, such as Dignāga in the 5th century and Dharmakirti in the 7th century, developed a type of atomism which defined the atoms which make up the world as momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy, though they also viewed all matter as being composed of these light

1. Light and Optics
Yield 4 Stars

2. Key Points
•8.1 Electromagnetic Spectrum (****)
–Electromagnetic Waves
–Color and Visible Spectrum
•8.2 Geometrical Optics (****)
–Reflection
–Refraction
–Lenses
–Dispersion
•8.3 Diffraction (**)
–Single Slit
–Slit-Lens System
–Multiple Slits
–X-Ray Diffraction
•8.4 Polarization (*)
–Plane-Polarized Light
–Circular Polarization

3. Electromagnetic Spectrum
•Electromagnetic Waves are transverse waves that
consist of an oscillating electric field and an
oscillating magnetic field
•The two fields are perpendicular to each other
and to the direction of propagation of the wave
•The electromagnetic spectrum is the range of
frequencies and wavelengths found in EM waves
•The visible spectrum runs from approximately
400nm (violet) to 700nm (red)

4. Electromagnetic Spectrum

5. Speed of light
•Electromagnetic waves vary in frequency and
wavelength, but in a vacuum, all
electromagnetic waves travel at the same
speed: speed of light
•

6. Geometrical Optics
•Reflection is the rebounding of incident light
waves at the boundary of a medium
•The law of reflection states that the incident
angle will equal the angle of reflection, as
measured from the normal

7. Law of Reflection

8. Spherical Mirrors
•Spherical mirrors have centers and radii of
curvature as well as focal points
–Concave mirrors
–Convex mirrors
–Plane mirrors

9. Optics Equation

10. Concave Mirrors
–Converging systems and can produce real,
inverted images or virtual, upright images,
depending on the placement of the objective
relative to the focal point

11. Convex Mirrors
•Diverging systems and will only produce
virtual upright images

12. Plane Mirrors
•Produce virtual, upright images; these images
are always the same size as the object. They
may be thought of as spherical mirrors with
infinite radii of curvature

13. Refraction
•Bending of light as it passes from one
medium to another
•Speed of light changes depending on index of
refraction of the medium. This speed causes
refraction.
•Amount of refraction depends on the
wavelength of the light involved; this
behavior causes dispersion of light through a
prism

14. Index of Refraction

15. Snell’s Law
•(SL=Law of refraction) states that there is an
inverse relationship between the index of
refraction and the sine of the angle of
refraction (measured from the normal).
•n1sin01=medium from which the light is
coming
•n2sin02+medium into which light is entering

16. Total Internal Reflection
•Occurs when light cannot be refracted out of
a medium and is instead reflected back inside
the medium
–This happens when light moves from a medium
with a higher index of refraction to a medium
with a lower index of refraction with a high
incident angle
–Minimum incident angle at which total internal
reflection occurs is called the “critical angle.”

17. Critical Angle
←-Critical Angle Equation

18. Lenses
•Refract light to form images of objects
•Thin symmetrical lenses have focal points on
each side
•Convex lenses are converging systems and can
produce real, inverted images or virtual, upright
images
•Concave lenses are diverging systems and will
only produce virtual upright images

19. Lensmaker’s Equation
•Lenses with non-negligible thickness require use
of the lensmaker’s equation
–N is the index of refraction of the lens material
–r1 is the radius of curvature of the first lens surface
–r2 is the radius of curvature of the second lens surface

20. Diffraction
•Bending and spreading out of light waves as
they pass through a narrow slit
•May produce a large central light fringe
surrounded by alternating light and dark
fringes with the addition of a lens
•INterference supports the wave theory of
light

21. Young’s double slit experiment
•Young’s double-slit experiment shows the
constructive and destructive interference of
waves that occur as light passes through
parallel slits, resulting in minima (dark
fringes) and maxima (bright fringes) of
intensity

22. Polarization
•In plane-polarized light, all of the light rays have
electric fields with parallel orientation.
•Plane-polarized light is created by passing
unpolarized light through a polarizer
•In circularly polarized light, all of the light rays
have electric fields with equal intensity but
constantly rotating direction
•Circularly polarized light is created by exposing
unpolarized light to special pigments or filters

23. Circular Polarization