## Waves,Properties and Their Applications.

4 Sep
1. 316/365 Revision Week: Partial Differential Equations (Photo credit: stuartpilbrow) English: Propagation of a plane compression wave (impulse); made with Scilab and Jasc Animation Shop 2.02 Deutsch: Vorstellung einer Longitudinalwelle (impuls); gemacht mit Scilab und Jasc Animation Shop 2.02 Français : Propagation d’une onde de compression plane (impulsion) ; créé avec Scilab et Jasc Animation Shop 2.02 (Photo credit: Wikipedia)  Refractive Indices (Photo credit: the_himay) English: Illustration of wavefronts in the context of Snell’s law. (Photo credit: Wikipedia)

Understand and use the terms amplitude, frequency, period, speed and wavelength

1. Identify the different regions of the electromagnetic spectrum and describe some of their applications.
1. Use the wave equation v = fλ.
1. Recall that a sound wave is a longitudinal wave which can be described in terms of the displacement of molecules.
1. Use graphs to represent transverse and longitudinal waves, including standing waves.
1. Explain and use the concepts of wavefront, coherence, path difference, superposition and phase.
1. Recognize and use the relationship between phase difference and path difference.
1. Explain what is meant by a standing (stationary) wave, investigate how such wave is formed, and identify nodes and antinodes.
1. Recognize and use the expression for refractive index 1μ2  = sin i/sin r = v1/v2 determine refractive index for a material in the laboratory, and predict whether total internal reflection will occur at an interface using critical angle.
1. Investigate and explain how to measure refractive index.
1. Investigate and explain how to measure the rotation of the plane of polarization.
1. Investigate and recall that waves can be diffracted and that substantial diffraction occurs when the size of the gap or obstacle is similar to the wavelength of the wave.
1. Explain how diffraction experiments provide evidence for the wave nature of elections.
1. Discuss how scientific ideas may change over time, for example, our ideas on the particle/wave nature of electrons.
1. Recall that, in general, waves are transmitted and reflected at an interface between media.
1. Explain how different media affect the transmission/reflection of waves travelling from one medium to another.
1. Explore and explain how a pulse-echo technique can provide details of the position and/or speed of an object and describe applications that use this technique.
1. Explain qualitatively how the movement of a source of sound or light relative to an observer/detector gives rise to a shift in frequency (Doppler Effect) and explore applications that use this effect.
1. Explain how the amount of detail in a scan may be limited by the wavelength of the radiations or by the duration of the pulses.
1. Discuss the social and ethical issues that need to be considered, e.g., when developing and trailing new medical techniques on patients or when funding a space mission.
Aside

## Astrophysics and Cosmology

2 Sep Intended as a replacement for File:Universe.svg and File:Universos.gif. Improvements: better dash patterns, more accurate curves (actual solutions of the Friedmann equations, not hand-drawn). (Photo credit: Wikipedia) Curve of Binding Energy Gamowtal Deutsches Museum (Photo credit: brewbooks) The path of a star with the mass of the Sun over Hertzsprung-Russell diagram during stellar evolution. (Photo credit: Wikipedia) The Big Crunch. The vertical axis can be considered as either plus or minus time. (Photo credit: Wikipedia) English: Graph of a function of total emitted energy of a black body j^{\star} proportional to the fourth power of its thermodynamic temeprature T , according to the Stefan–Boltzmann law. In blue is a total energy according to the Wien approximation, equals j^{\star} / \zeta(4) \approx 0.923938 j^{\star} . (Photo credit: Wikipedia)

1. use the expression F = Gm1m2/r2
2. derive and use the expression g = −Gm/r2 for the gravitational field due to a point mass
3. recall similarities and differences between electric and gravitational fields
4. recognize and use the expression relating flux, luminosity and distance F = L/4πd2 and the application to standard candles
5. explain how distances can be determined using trigonometric parallax and by measurements on radiation flux received from objects of known luminosity (standard candles)
6. Recognize and use a simple Hertzsprung-Russell diagram to relate luminosity and temperature. Use this diagram to explain the life cycle of stars
7. Recognize and use the expression L = σT4 x surface area, (for a sphere L = 4πr2σT4) (Stefan-Boltzmann law) for black body radiators.
8. recognize and use the expression: λmaxT = 2.898 x 10-3 m K (Wien’s law) for black body radiators
9. recognize and use the expressions z = Δλ/λ ≈ Δf/f ≈ v/c for a source of electromagnetic radiation moving relative to an observer and v = H0d for objects at cosmological distances
10. be aware of the controversy over the age and ultimate fate of the universe associated with the value of the Hubble Constant and the possible existence of dark matter
11. explain the concept of nuclear binding energy, and recognise and use the expression ΔE = c2Δm and use the non SI atomic mass unit (u) in calculations of nuclear mass (including mass deficit) and energy
12. describe the processes of nuclear fusion and fission
13. explain the mechanism of nuclear fusion and the need for high densities of matter and high temperatures to bring it about and maintain it
14.

## Unit 5. Oscillation

1 Sep   English: This animation depicts a simple pendulum consisting of a mass suspended by a light string and released from a small lateral displacement. If the amplitude is very small and the system is undamped, it behaves as a simple harmonic oscillator. (Photo credit: Wikipedia)

Oscillations

1. Recall that the condition for simple harmonic motion is F = –kx, and hence identify situations in which simple harmonic motion will occur    Spec-119

2. Recognize and use the expressions a = – ω2x,           a = –2 cos ωt, v = sin ωt, x = Acos ωt and      T = 1/f = 2π/ω as applied to a simple harmonic oscillator Spec-120.

 3. obtain a displacement – time   graph for an oscillating object and recognize that the gradient at a point   gives the velocity at that point  Spec-   121

4. Recall that the total energy of an undammed simple harmonic system remains constant and recognize and use expressions for total energy of an oscillator. Spec-122

5. Distinguish between free, damped and forced oscillations.  Spec- 123

6. Investigate and recall how the amplitude of a forced oscillation changes at and around the natural frequency of a system and describe, qualitatively, how damping affects resonance. Spec-124

7. Explain how damping and the plastic deformation of ductile materials reduce the amplitude of oscillation.                                                                             Spec 125.

## Mechanics AS

22 Aug Three dimensional Cartesian coordinate system with the x-axis pointing towards the observer (Photo credit: Wikipedia) The analysis of projectile motion is a part of classical mechanics. (Photo credit: Wikipedia)

Unit 1 Topic 1 Mechanics

Target sheet

I can:

1.  Equation of uniformly accelerated motion.

2. Displacement time graph

3. Velocity time graph.

8. Resolving a vector onto X-axis and Y-axis.

9. Air resistance and solid friction.

10. Static and Kinetic Equilibrium.

11. Coplanar forces.

## Electric and Magnetic Fields.

22 Aug  English: Fleming’s left hand rule shows the direction of the thrust on a conductor carrying a current in a magnetic field. (Photo credit: Wikipedia)

 Statement Spec ref Comments explain what is meant by an   electric field and recognise and use the expression electric field strength E   = F/Q 83 draw and interpret diagrams using   lines of force to describe radial and uniform electric fields qualitatively 84 use the expression F = kQ1Q2/r2,   where k = 1/4πε0 and derive and use the expression E = kQ/r2   for the electric field due to a point charge 85 investigate and recall that   applying a potential difference to two parallel plates produces a uniform   electric field in the central region between them, and recognise and use the   expression E = V/d 86 investigate and use the   expression C = Q/V 87 recognise and use the expression W   = ½ QV for the energy stored by a capacitor, derive the expression   from the area under a graph of potential difference against charge stored,   and derive and use related expressions, for example, W = ½ CV2 88 investigate and recall that the   growth and decay curves for resistor–capacitor circuits are exponential, and   know the significance of the time constant RC 89 recognise and use the expression Q   = Q0 e−t/RCand derive and use   related expressions, for exponential discharge in RC circuits, for example, I   = I0e−t/RC 90 explore and use the terms   magnetic flux density B, flux Φ and flux linkage NΦ 91 investigate, recognise and use   the expression         F = BIl   sin θ and   apply Fleming’s left hand rule to currents 92 recognise and use the expression F   = Bqv sin θ and apply Fleming’s left hand rule to charges 93 investigate and explain   qualitatively the factors affecting the emf induced in a coil when there is   relative motion between the coil and a permanent magnet and when there is a   change of current in a primary coil linked with it 94 investigate, recognise and use   the expression ε = −d(NΦ)/dt   and explain how it is a consequence of Faraday’s and Lenz’s laws 95

## The Cepheid Variable.

22 Aug English: The oldest star of our Galaxy: HE 1523-0901 (Photo credit: Wikipedia)  Wireless Temperature Sensor Module uploading to emoncms via Nanode (Photo credit: Nathan Chantrell) This ZAMS mass-luminosity table was generated using data from the isocrone calculation tool of Lionel Siess. The metallicity (Z) is 0.02 and the axis units use solar values. Note that the present-day Sun is more luminous than when it first joined the main sequence. (Photo credit: Wikipedia)

6. b) The graphs show the sensitivity of a particular brand photographic film and that of a charge coupled device, CCD, to different parts of the e.m spectrum.

The surface temperature of a star can be calculated once the wavelength of the peak of its spectrum (λmax) is known.  Use the graphs to explain why photographic film would be less suitable than CCDs for determining (λmax) for a star which radiates mainly in the visible region (400nm-700nm) of the e.m spectrum.

6b) (Answer.) The bandwidth of the film is from 350nm to 700nm whereas that of the CCD is from 300nm to 1000nm. The CCD is more suitable because the   relative sensitivity of the film is not uniform and ranges from 0.5 to a maximum of 1.0. The CCD is much better in this regard for it is uniform and close to 1 for the entire spectrum.

6c) State what happens to the hydrogen ‘burning’

6c) (Answer) The hydrogen fuses to become Helium and that is more stable.  When time will allow the star will be low in fuel and it will expand slightly.  This expansion causes the temperature to fall and the star becomes a red giant.

Why is a red giant more luminous than the main sequence star from which it originated, even though its temperature is lower?                      (1)

The luminosity depends upon the square of the radius and the 4th of the temperature.  The red giant expands more hence the radius factor plays a more important role than the temperature factor.

6d). Describe how observations of Cepheid variable stars are used to estimate the distance to nearby galaxies.

A longer time period for oscillation meant an intrinsically brighter star.  Astronomers then took this relationship and used it to determine the luminosity of variable stars at much greater distances.  From the luminosity, the distance to these stars can be determined using our expression for the radiant energy flux observed here on Earth.  Hence the estimate to the distance can be measured.

e)    Explain the meaning of the term binary system (1)

It is a star system which is made up of two stars having a common centre.

f)     At A C and E the light intensity  gets lower due to the fact that  shadow of one of the stars falling on the other.

g)    The dip at A is much smaller due to the fact that the other star is smaller. Whereas the dip at C is larger because the opposing star is larger.

h)   Estimate the orbital period of this binary.

From 2 hours to 24 hours or 22 hours.

Estimate the orbital period of this binary. (1)

i)     From B to D: 8 to 19 hours or 11 hours.

1. Annual parallax method

tan θ = r/ d.

It is not a suitable method because it uses the parallax method hence it cannot be used for distant stars more than 650 ly.

1. The two ways the white      dwarfs differ from the mainline stars are there is intense gravitational      pressure.  This makes it very small      in size.

Describe what happens to a star when it becomes a white dwarf?

Its strong gravitational field outweighs the fusion. And becomes very low luminous star,

1.  40,0000K , 20,000K  10,000K, 5000K, 2500K

b) L = 1

lower left hand corner.

L= 104

They burn out quickly intense nuclear radiation.

1.  The surface temperature could be same but      then again not for the colour is dependent upon the surface area and the      temperature.
1. F = L/ A

Deneb has greater surface area. The luminosity is much larger,

1.  Work it out your self.

## The Nature of Particles

21 Aug  Black body radiation for T=287K, which is the temperature of the earth. (Photo credit: Wikipedia) English: Black body curves of Planck for various temperatures and comparison with classical theory of Rayleigh-Jeans. Italiano: Confronto fra le curve del corpo nero della teoria di Planck e della teoria classica di Rayleigh-Jeans. (Photo credit: Wikipedia)

The nature of particle.

1.Thomson concluded that those cathode rays were made up of particles.

2. Max Planck was trying to find out a model to understand the way in which a black body emits radiation.

3. Black body is perfect emitter and absorber of electromagnetic radiation.

4. He found that this was possible only if he had assumed radiations were emitted in packets.

5. Plank’s idea was not understood until Einstein, 1905 showed that black body radiation could be understood better if it was assumed that the radiation itself was quantised,  consisting of particle like packets of energy.

6.Each is referred to as photon.

Ultraviolet catastrophe:  Classical physics can predict that black body radiation based on long wavelength but not at short wavelengths, leading a disagreement that physicist calls as U.V catastrophe.

Radiation Flux —Do the worked out example.