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PHYSICS

PHYSICS. COURSE CODE: PH101. COURSE MATERIALS. PHYSICAL OPTICS RELATIVITY RADIATION ATOMIC STRUCTURE STATISTICAL DISTRIBUTIONS LASERS. TEACHING PROCESS. The whole course will be covered through Lectures Tutorials Laboratory.

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PHYSICS

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  1. PHYSICS COURSE CODE: PH101

  2. COURSE MATERIALS • PHYSICAL OPTICS • RELATIVITY • RADIATION • ATOMIC STRUCTURE • STATISTICAL DISTRIBUTIONS • LASERS

  3. TEACHING PROCESS • The whole course will be covered through • Lectures • Tutorials • 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.

  4. 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.

  5. PHYSICAL OPTICS

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

  7. 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

  8. 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

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

  10. Physical Optics

  11. Waves All Around Us!

  12. 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.

  13. Wave 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.

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

  15. Physical description of a wave

  16. 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.

  17. Amplitude is a nonnegativescalar measure of a wave's magnitude of oscillation. The y is the amplitude of the wave. The wavelength is the distance between repeating units of a wave pattern

  18. 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. positions of the peaks (X), troughs (Y) and zero-crossing points (Z) coincide. The phase difference of the waves is thus zero

  19. 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.

  20. 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.

  21. 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  =

  22. 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

  23. 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

  24. What is light? Electromagnetic radiation of any wavelength.

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

  26. 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.

  27. 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.

  28. 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.

  29. 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

  30. Virtual source S1 S S2 P Monochromatic source D DIVSION OF WAVE FRONT

  31. II I d a c b DIVISION OF AMPLITUDE

  32. 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

  33. 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

  34. 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.

  35. Two waves that are in phase,with amplitudes A1 and A2. Their troughs and peaks line up and the resultant wave will have amplitude A = A1 + A2. 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 = |A1 − A2|. If A1 = A2 the resultant amplitude will be zero. This is known as destructive interference.

  36. combinedwaveform wave 1 wave 2 Two waves in phase Two waves 180° outof phase

  37. P S1 yn d/2 d O d/2 S2 D Let y1 and y2 are the displacements of two waves coming from S1 and S2 L

  38. is the phase difference between two waves reaching At P from S1 and S2, a be the amplitude of wave.

  39. In each case n = 0,1,2….

  40. For incoherent light =sum of intensity of constituent waves.

  41. 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.

  42. Young’s Double slit experiment

  43. 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. (The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns.

  44. S1 yn d/2 O d/2 S2 D THE INTERFERENCE FRINGES P d At point P for maxima we must have S2P – S1P = n, n = 0,1,2,3… L

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