PHYSICS COURSE CODE: PH101

COURSE MATERIALS 1.PHYSICAL OPTICS 2.RELATIVITY 3.RADIATION 4.ATOMIC STRUCTURE 5.STATISTICAL DISTRIBUTIONS 6.LASERS

TEACHING PROCESS The whole course will be covered through 1.Lectures 2.Tutorials 3.Laboratory The topics will be covered in the lectures. Assignments in the form of Questions will be given. Students have to complete the assignments through discussion in tutorials. Class tests will be conducted during tutorials.

Evaluation scheme There will be three tests all over the semester. 20 marks for the Test-I. 25 marks for the Test-II. 30 marks for the TEST-III. 25 marks for internal assessment and class tests. 100 marks for the laboratory work. Evaluation will be done through regular assessment of practical and viva-voca.

PHYSICAL OPTICS

BOOKS: OPTICS, Eugene Hecht, Pearson Education. OPTICS, Ajay Ghatak. Fundamental of Optics, Jenkins & White. A. Beiser, Concepts of Modern Physics,

Optical Recording Media types: –Compact Disc (CD) –Digital Video/Versatile Disc (DVD) Reading technique: –Reflect laser light from optical surface –Measure reflected intensity to obtain information

Techniques Laser light is focused on disc aluminum layer Reflection is weaker from ridge than flat Reflected light is directed to photodiodes Light intensity indicates ridges or flats

Most of the above applications need some optical phenomena Interference, Diffraction, Polarization Physical Optics OPTICS

Physical Optics Wave nature of light InterferenceDiffractionPolarization

Waves All Around Us!

Waves are everywhere. Sound waves, visible light waves, radio waves, microwaves, water waves, sine waves, cosine waves, telephone chord waves etc. There are a variety of phenomenon in our physical world which resemble waves so closely that we can describe such phenomenon as being wavelike.

A wave is a disturbance that propagates, carrying energy, which can travel through either in a medium or through vacuum, waves can transfer energy from one place to another without any displacement of the particles of the medium. Wave

Waves are characterized by crest (highs) and trough(lows) THERE ARE TWO TYPES OF COMMON WAVES. I)SOUND WAVE II)LIGHT WAVE

Physical description of a wave

waves of various frequencies; the lower waves have higher frequencies than those above. Frequency is the measurement of the number of times that event occurs repeatedly per unit time. To calculate the frequency, one fixes a time interval, counts the number of occurrences of the event within that interval, and then divides this count by the length of the time interval.measurementtime

Amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation. The y is the amplitude of the wave.nonnegativescalar waveoscillation The wavelength is the distance between repeating units of a wave patternwave

Phase The phase of a wave relates the position of a feature, typically a peak or a trough of the waveform, to that same feature in another part of the waveform.waveform positions of the peaks (X), troughs (Y) and zero-crossing points (Z) coincide. The phase difference of the waves is thus zero

The phase difference between two signals of the same frequency can be thought of as a delay or advance in the start of one signal's cycle with respect to another.phasesignals frequency

Phase difference is expressed in degrees from 0 to 360. If the difference is 180 degrees then the two signals are said to be in antiphase: they are equal but opposite, and if added together will sum to zero. If the phase difference is 90 degrees then the signals are said to be in quadrature.quadrature

Phase difference and path difference If the phase difference between two waves is 2  then the path difference between that two waves is. Let for a path difference x, the phase difference is . We know that for a path difference, phase difference = 2  so, for path difference x, the phase difference = So, phase difference  =

Angular frequency angular frequency ω (also called angular speed) is a scalar measure of rotation rate. Angular frequency is a measure of how fast an object is rotating

The period T of the motion is the time taken for the particle to go through one full circle. T = 2  /  Frequency f =1/T

What is light? Electromagnetic radiation of any wavelength.

The three basic dimensions of light :dimensions intensity (or amplitude, perceived by humans as the brightness of the light),intensityamplitude frequency (or wavelength, perceived by humans as the color of the light),frequencywavelength color polarization (or angle of vibration and not perceptible by humans under ordinary circumstances)polarization

PRINCIPLE OF SUPERPOSITION principle of superposition states that the net displacement at a given place and time caused by two or more waves traversing the same space is the vector sum of the displacements which would have been produced by the individual waves separately.

Two wave pulses are travelling, one is moving to the right, the other is moving to the left. They pass through each other without being disturbed, and the net displacement is the sum of the two individual displacements.

COHERENT SOURCES Sources emitting light waves of the same frequency, nearly same amplitude and are always in phase with each other or having a constant phase relationship between them, means that two sources must emit radiations of the same wavelength.

In practice it is not possible to get independent Two sources which are coherent. But two virtual Sources formed from one single source can act as Coherent source. Two ways to get coherent source Division of wave front : waves from two sources are formed from a single source Division of amplitude : waves from two sources are formed from a single source due to reflection and Refraction. One of these source is real other virtual source

P D S Monochromatic source S1S1 S2S2 Virtual source DIVSION OF WAVE FRONT

a b c d I II DIVISION OF AMPLITUDE

INTERFERENCE Interference is the superposition of two or more coherent waves resulting in a new wave pattern. There are two types of interference: Constructive Interference Destructive Interference

Conditions of Interference The interfering waves should be coherent The interfering waves must be of same wavelengths Two waves must have the same state of polarization to get fringes of maximum contrast

Constructive and destructive interference If the two waves have the same amplitude A and wavelength the resultant waveform will have amplitude between 0 and 2A depending on whether the two waves are in phase or out of phase. If the two waves are in phase, interference will be constructive. If the two waves are out of phase, interference will be destructive.

Two waves that are in phase,with amplitudes A 1 and A 2. Their troughs and peaks line up and the resultant wave will have amplitude A = A 1 + A 2. This is known as constructive interference. If the two waves are 180° out of phase, then one wave's crests will coincide with another wave's troughs and so will tend to cancel out. The resultant amplitude is A = |A 1 − A 2 |. If A 1 = A 2 the resultant amplitude will be zero. This is known as destructive interference.

combined waveform wave 1 wave 2 Two waves in phase Two waves 180° out of phase

S1S1 S2S2 L P O D d ynyn d/2 Let y 1 and y 2 are the displacements of two waves coming from S 1 and S 2

 is the phase difference between two waves reaching At P from S 1 and S 2, a be the amplitude of wave.

In each case n = 0,1,2….

For incoherent light = sum of intensity of constituent waves.

Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). As time progresses, the wave fronts would move outwards from the two centers, but the dark regions (destructive interference) stay fixed.

Young’s Double slit experiment

Experiment consists of letting light passes through two slits producing fringes on a screen. These fringes or interference patterns have light and dark regions corresponding to where the light waves have constructively and destructively interfered.lightinterference (The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns.experimentelectronsatoms

L P d S1S1 S2S2 O D ynyn d/2 At point P for maxima we must have S 2 P – S 1 P = n, n = 0,1,2,3… THE INTERFERENCE FRINGES

If d  <D then S 2 P  S 1 P  D and thus S 2 P+S 1 P=2D  

So we get, for dark and bright fringes Distance between any two consecutive bright fringes

Fringe width 

Seperation between dark and bright fringes O is equidistant from S 1 and S 2 so light waves superposed at O are in phase so light intensity at O will be maximum.

At O we observe the central bright fringe. For this fringe n=0 y = 0. so central bright fringe will be referred as zeroth order bright fringe. At n=1 we have y= 1 D/d, this is the first order bright fringe. At n=0 we observe first dark fringe at y = D/2d. So at n=0 we have the first order dark fringe.

Dark areas = Troughs (valleys) Light aresa = Crests (peaks)