Page 307 - General Knowledge

GENERAL KNOWLEDGE 2019

C = specific heat of the substance and
= change in temperature.

Heat flow between bodies at different temperatures
 When a body at a higher temperature is in direct contact with a body at a lower temperature
heat energy flows between the two bodies.
 The heat energy flows from the hotter body to the cooler body until they are both at the same
temperature.
 If we assume that there is no heat loss to the surroundings as the heat flow occurs then,
 Heat lost by hotter body = Heat gained by cooler body.
 Therefore, when two or more bodies are in contact they have or will achieve the same
temperature.
 When doing problems where substances at different temperatures are being put together
(i.e. mixing substances at different temperatures) always
 Assume that there is no heat loss to the surroundings unless otherwise told and
 Always use the equation
 Heat lost by hotter body/bodies = Heat gained by cooler body/bodies.

7. LIGHT

 Light is an electromagnetic radiation within a certain portion of the electromagnetic spectrum.
 The word usually refers to visible light, which is visible to the human eye and is responsible
for the sense of sight.
 It is a special type of wave and what we know as light or visible light is actually a type of
something called Electromagnetic radiation.
 When something creates energy, it also emits radiation.
 Depending on the amount of energy, the object will emit different types of electromagnetic
radiation.
 When we studied mechanical waves, they were all transferred through a medium.
 Electrons in materials are vibrated and emit energy in the form of photons, which propagate
across the universe.
 Photons have no mass, but are pure energy.
 Electromagnetic Waves are waves that are made up of these ―photons‖.
 When these photons come in contact with boundaries, E-M waves interact like other waves
would.
 The greater the frequency of an E-M wave, the more crests pass a point in a certain amount
of time, therefore the more photons pass that point.
 This means that more energy moves past that point in a certain amount of time or that the
wave contains more energy.
Polarization
 Polarization is a phenomenon of light that is used in sun-glasses and 3-D movies.
 Light vibrates in all directions.
 A polarizing filter acts like a picket fence. It only lets certain direction vibrations pass through it.

Properties of light
 The sun radiates light, electric lights brighten our darkness, and many other uses of light
impact our lives daily.

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