Physics Form 4

Yaliyomo

1. 1. Waves I: Wave Motion and Sound

   Majaribio 1 Maswali 17

   Maelezo ya mada

   • What is a wave? Transverse and longitudinal waves
   • Describing waves: amplitude, wavelength, frequency and speed
   • Reflection, refraction, diffraction and interference of waves
   • Sound: production, propagation and echoes
   • Characteristics of sound; vibrations in strings and pipes
   • Summary

   What is a wave? A wave is a disturbance that transfers energy from one place to another without transferring matter. When a stone is dropped into a pond, ripples spread outwards, but a floating leaf only bobs up and down. Mechanical waves (water waves, sound, waves on a rope) need a medium; electromagnetic waves…

2. 2. Waves II: Electromagnetic Waves

   Majaribio 1 Maswali 16

   Maelezo ya mada

   • The nature and properties of electromagnetic waves
   • The electromagnetic spectrum: sources, uses and dangers
   • Wave properties of light: diffraction, interference and polarisation
   • Electromagnetic waves in communication
   • Summary

   Electromagnetic waves Electromagnetic (EM) waves are transverse waves made of changing electric and magnetic fields vibrating at right angles to each other and to the direction of travel. They are produced by accelerating electric charges. All EM waves: travel through a vacuum at the same speed, c = 3 × 10 8 m/s ; are…

3. 3. Electromagnetism

   Majaribio 1 Maswali 17

   Maelezo ya mada

   • The magnetic effect of an electric current
   • Electromagnets and their uses
   • Force on a current in a magnetic field (the motor effect)
   • The d.c. electric motor
   • Electromagnetic induction and generators
   • Transformers and the transmission of electrical power
   • Summary

   Magnetic effect of a current Oersted discovered that a current in a wire produces a magnetic field around it. For a straight wire the field lines are concentric circles; their direction is given by the right-hand grip rule : grip the wire with the right hand, thumb pointing along the conventional current, and the…

4. 4. Radioactivity

   Majaribio 1 Maswali 17

   Maelezo ya mada

   • The nucleus, nuclides and isotopes
   • Radioactive decay: alpha, beta and gamma radiation
   • Half-life
   • Detecting radiation and background radiation
   • Uses, dangers and nuclear energy
   • Summary

   The nucleus An atom has a small, dense nucleus containing protons (positive) and neutrons (neutral), together called nucleons , with electrons around it. The atomic number Z is the number of protons; the mass number A is the number of protons plus neutrons. A nuclide is written A Z X; e.g. 23 11 Na has 11 protons and…

5. 5. Thermionic Emission

   Majaribio 1 Maswali 15

   Maelezo ya mada

   • Thermionic emission and cathode rays
   • Energy of electrons, deflection and the diode valve
   • The cathode ray oscilloscope (CRO)
   • X-rays
   • Summary

   What is thermionic emission? Thermionic emission is the release of electrons from the surface of a metal when it is heated to a high temperature. Heating gives the free electrons in the metal enough energy to escape from the surface. The minimum energy needed is called the work function . Metals with low work functions…

6. 6. Basic Electronics

   Majaribio 1 Maswali 16

   Maelezo ya mada

   • Semiconductors and doping
   • The p-n junction diode
   • Rectification and smoothing
   • LEDs, LDRs, thermistors and capacitors
   • The transistor as an amplifier and a switch
   • Summary

   Conductors, insulators and semiconductors Materials are grouped by how well they conduct. Conductors (metals) have many free electrons. Insulators (rubber, glass) have almost none. Semiconductors such as silicon and germanium are in between: they conduct poorly when pure and cold, but their conductivity rises with…

7. 7. Elementary Astronomy

   Majaribio 1 Maswali 16

   Maelezo ya mada

   • The universe, galaxies, stars and constellations
   • The solar system
   • Motions of the Earth: day, night, years and seasons
   • The Moon: phases, eclipses and tides
   • Summary

   What is astronomy? Astronomy is the scientific study of heavenly bodies (stars, planets, moons, comets, galaxies) and of the universe as a whole. People have long used the sky to tell the time and seasons, for example farmers watching star patterns to know when the rains will come, and sailors on the Indian Ocean using…

8. 8. Geophysics

   Majaribio 1 Maswali 15

   Maelezo ya mada

   • Structure of the Earth and plate tectonics
   • Earthquakes and seismic waves
   • Volcanoes and the Earth's magnetic and gravitational fields
   • The atmosphere and the greenhouse effect
   • Summary

   What is geophysics? Geophysics is the branch of physics that studies the Earth – its structure, its magnetic and gravitational fields, earthquakes, volcanoes and the atmosphere – using the methods of physics. Structure of the Earth Crust – the thin, solid outer layer (about 5–10 km under oceans, up to 70 km under…