```Doppler Effect                                            This effect, where there is a change in
frequency and wavelength, is called the
  It is named after the Austrian physicist               Doppler Effect.
Christian Doppler, who proposed it in                 When a source moves towards an
1842 in Prague.                                        observer, the observed wavelength
  You may have noticed that when an                      decreases and the frequency increases.
ambulance or police car goes past, its siren          When a source moves away from an
is high-pitched as it comes towards you,               observer, the observed wavelength
then becomes low-pitched as it goes away.              increases and the frequency decreases.
HEAT & TEMPERATURE
Heat                                                     Body temperature can rise to 105 degrees
if working outside in a heat wave. Death
  It is a form of energy and measures the                occurs usually when a body temperature
total energy of all molecules in the                   reaches 107.6.
substance.
   You’ll lose weight in the heat.
  It is a total kinetic energy of all molecules
in a substance.                                       The average temperature on Mars is -63C.
  Its units are Calorie (cal), Kilocalorie              Good heat conductors: Gold, Copper,
(kcal) or Joule (J). Its CGS unit is the erg           Silver, Iron, Aluminum, Nickel, Zinc &
= 10-7 joule.                                          most other metals
  1 cal = 4.18 joule                                    Bad heat conductors: Plastic, Bakelite,
  1 kcal = 1000 cal                                      Styrofoam, Air, Water, Rubber, Cotton,
Silk, Marble, Wood, Mica
Temperature
   When lightning strikes it can reach up to
  It is a measure of degree of hotness or                30,000 degrees Celsius (54,000 degrees
coldness of a body.                                    Fahrenheit)
  The unit of degree Celsius or Kelvin or               Room temperature is defined as between
degree Fahrenheit.                                     20° to 25°C (68° to 77°F)
  Two bodies cannot be in thermal                       When water freezes it expands by 9%
equilibrium if they are at different
   Hot water freezes quicker than cold water
Temperature.
  It is a measure of average kinetic energy             Normal body temperature is 37°C (99°F)
of molecules in a substance.                          The center of the Sun is approximately 15
  The formula relating all temperature scales            million°C
is
Pyrometer
C F  32 R K
           
5      9      4 5                                    It is an instrument for measuring
temperature.
Facts about Heat and Temperature                         Optical pyrometer : It determines the
temperature of a very hot object by the
  The highest temperature ever recorded on               color of the visible light it gives off.
Earth was 136 Fahrenheit (58 Celsius) in              Radiation pyrometer : It determines the
the Libyan desert. The coldest temperature             temperature of an object from the radiation
ever measured was -126 Fahrenheit (-88                 (infrared and, if present, visible light)
Celsius) at Vostok Station in Antarctica.              given off by the object.
18
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