physics digest

ELECTROMAGNETIC WAVES Electromagnetic wave : is self-propagating transverse oscillating wave of electric and magnetic fields.  Electromagnetic radiation (Em radiation or Emr) is a form of energy emitted and absorbed by charged particles, which exhibits wave - like behavior as it travels through space. EMR has both electric and magnetic field components which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. EMR is classified according to the frequency of its wave. The electromagnetic spectrum, in order of decreasing wavelength and increasing frequency, we have  →  Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. SOURCES OF ELECTROMAGNETIC WAVES Type Source Typical wavelength Gamma ray  Emitted by Radioactive sources 10  -14 X – ray  Produced by ...

FRICTION When a solid is in contact with another, the roughness of their surface prevents them from sliding freely over one another. Such action is brought about by the effect of friction. Friction is defined as a force, which acts at the surface of separation between two objects in contact and tends to oppose the motion of one over the other. Frictional forces act tangential to the surface of separation between two bodies in contact. Friction is a force of opposition. TYPES OF FRICTION There are two major types of friction namely: a.              Static friction  b.              Kinetic or dynamic friction  Static friction : This is the maximum force that must be overcome before a body can just start to move over another. Kinetic or dynamic friction : This is the force that must be overcome so that a body can move with uniform speed over a...