Skssknowledge

Wave Optics -: Learning objectives   -: Electromagnetic waves, Plane waves.    -: Velocity of electromagnetic waves.    -: Properties of electromagnetic waves.    -: Hertz experiment.    -: Electromagnetic spectrum.    -: Huygen's wave theory, Huygen's principle, explanation of reflection and refraction.     -: Interference, Young's double slit experiment, Lloyd's single mirror, Fresnel's bi-prism experiment.  1. ELECTROMAGNETIC WAVES James Clerk Maxwell, one of the pioneers in the field of electromagnetic waves, gave his theory of electromagnetic waves in 1865. An electromagnetic wave is composed of oscillating electric and magnetic fields which oscillate in manually perpendicular planes. These two planes, besides being perpendicular to each other, are also perpendicular to the direction of propagation of the wave. Using his equations, called Maxwell's equations , he derived the formula for speed of electromagne...

-: HEALTH AND DISEASE Health can be defined as "a state of body when all the organs and organ systems are functioning properly in their physiology and a perfect balance is maintained between the environment and the body. " It can also be defined as, "a state of complete physical, mental and social well being" . So health is more than just absence of disease only.               Disease is the "sickness of the body and the mind" . It is the malfunctioning of the body due to some reasons. So disease can be defined as, "a condition of the body or its parts in which the functions are distributed or deranged" . -: WHAT CAUSES DISEASE ? The agent of a disease is a substance or a force which causes disease due to its excessive presence or absence. These agents can be of different types. 1. Biological Agents or Pathogens . Different microorganisms like bacteria, viruses, fungi, protozoans, helminths, etc. are called pathogens. 2. Nutrient Agents . The exc...