such a good presentation

1. DIFFRACTION
&
WAVE THEORY OF LIGHT

2. DIFFRACTION
 INTRODUCTION:
 Diffraction is the phenomenon that occurs when waves bend
around objects; specifically when passing through a gap and spreading
out at the end. Francesco Maria Grimaldi an Italian scientist was the
first to observe and identify this phenomenon.

6. WAVE THEORY OF LIGHT

7.  According to particle nature of light that was presented by
Newton. Newton said that light is actually in the form of small
packets. Newton generally said particles to these small packets. And
the light are in the form of particles, and he named it corpuscles. And
corpuscles are also known as particles of light. Newton said that the
nature of light is corpuscular and the particles of light are travel in
the form of packets. This known as corpuscular theory.

8.  After this a physics scientist HUYGEN’S comes and he presented
that the light are in the form of wave. It is not in the form of particles.
 We have two forms in which object travel,
 First one “The object travel in the form of wave” that is the theory of
HUYGEN’S,
 Second one is that “The objects travel in the form of packets or
corpuscles” which is the theory of Newton.

9. Physics presntation
Presenting team
Abdullah
Adnan sher
Ijaz ahmad
Hassan farooq
Muhammad abbas

10. Carpuscular theory which is the theory of newton that was rejected
because it includes some points that are wrong after sometime.
Huygens presented that the light travel in the form of waves.
According to the physicians whenever any wave moves, it required a
medium to travel from place to another.
Such as:

11.  Water waves its medium is water because water waves travel on
water.
 Sound waves its medium is Air, Solid and Liquid because sound
waves cannot move without these mediums

12.  So when light presented in the form of waves so physicts said that
in universe all space around us their exist a medium that named as
“AETHER”.
 In the Aether a light waves travel. Without this medium a light
wave cannot move.

13.  In figure we showed light in the form of
waves.
 Huygens presented his theory that light
can travel in the form of wave, Not in the
form of particles so for the support of
Huygens theory the best evidence is
interference phenomenon.

14.  Interference of light:
 “The process in which two or more light, or electromagnetic waves
of the same frequency combine to reinforce or cancel each other, the
amplitude of the resulting wave being equal to the sum of the
amplitudes of combining waves.”
Interference have two types :

15.  Constructive interference:
When two waves meet in such a way that their crests line up
together, then it's called constructive interference. The resulting
wave has a higher amplitude.
 Destructive interference:
when the crest of one wave meets the trough of another, and the
result is a lower total amplitude

16.  The phenomenon of interference doesn’t occur in particles because it
is general property of wave.
 Diffraction and interference are those properties which only occur in
waves.
 When light observed interference phenomenon so from it is proved
that the light is actually in the form of waves , not in particles form. And
this experiment was done by THOMAS YOUNG . so THOMAS
YOUNG supported the HUYGEN’S THEORY.

17.  Another scientist “MAXWELL” proved that the light is actually
the form Electromagnetic waves and speed of light is equal to the
speed of electromagnetic waves and it is denoted by “C”. and its value
is 3 x 10^8 m/s in the vaccum
 And its speed is different in different medias.

18.  So it is the theory that presented HUYGENS against NEWTON
that the light travels in the form waves , not in the form of particles
form
 Huygens presented this theory and other scientists proof it that
the light are in the form of wave

19. LIGHT WAVE THEORY
 Light can exhibit both a wave theory, and a particle theory at the same
time. Much of the time, light behaves like a wave. Light waves are also
called electromagnetic waves because they are made up of both electric
(E) and magnetic (H) fields. Electromagnetic fields oscillate perpendicular
to the direction of wave travel, and perpendicular to each other. Light
waves are known as transverse waves as they oscillate in the direction
traverse to the direction of wave travel.

21. WAV E S H AV E T W O I M P O R T A N T C H A R A C T E R I S T I C S -
WAV E L E N G T H A N D F R E Q U E N C Y.
 Wavelength:
 This is the distance between peaks of a wave. Wavelengths are measured in
units of length - meters, When dealing with light, wavelengths are in the order
of nanometres (1 x 10-9
)
 Frequency:
This is the number of peaks that will travel past a point in one second.
Frequency is measured in cycles per second. The term given to this is Hertz
(Hz) named after the 19th century discoverer of radio waves - Heinrich Hertz.
1 Hz = 1 cycle per second

22. HUYGENS PRINCIPLE
 Huygens’s Principle states that every point on a wavefront is a
source of wavelets.
 These wavelets spread out in the forward direction, at the same
speed as the source wave. The new wavefront is a line tangent to all
of the wavelets.

24. FIGURE OF WAVE THEORY
RELATING TO DIFFRACTION:

25. Thank
you