Heat can be transferred through a material from area to another in three different ways: conduction, convection and radiation.
Conduction mostly occurs in solids, however, it can still take place in fluids. It is a process within a substance when it is heated that causes its individual atoms to vibrate rapidly, colliding into neighbouring atoms. (Eureka! Episode 24 Conduction, 1978) This increased speed of vibration and heat is directly transmitted through substances from atom to atom. Another method of heat transfer is convection, which causes particles to speed up, expand and become less dense. (Eureka! Episode 27 Convection, 1978) This movement pushes the colder, denser particles to sink and draw closer to the heat source, consequently resulting in heat transfer. A third way heat can be transferred is through radiation, a form of pure heat energy transmitted in waves or a stream of particles that do not need a medium to transfer heat and can occur anywhere in a vacuum. (Physics Classroom, 2018) Insulation is a barrier that minimises the transfer of heat energy from one material to another by reducing the effects of conduction and convection.
(Kurtus, 2014) Less dense substances – such as water, plastic and rubber are better insulators because its particles are furtherer apart, decreasing the effectiveness of conduction. (Physics Classroom, 2018) On the other hand, thermal conductivity is the degree to which a material can conduct heat. Denser materials, which include metal and graphite, are effective conductors because the closer the atoms are together, the quicker it is to conduct heat. (Physics Classroom, 2018) The reason why metals are effective conductors because the electrons of its individual atoms do not seem to have an attraction to the nucleus, shooting extremely rapidly at all different directions. (Eureka! Episode 24 Conduction, 1978) When metals are heated, not only does the free electrons vibrate faster but it also collides with other atoms with an increased rate and force. There are three different ways light can act when it hits a surface: reflection, absorption of light and transmission.
Reflection is the change in direction of a wave at an interface between two dissimilar media so that the wavefront returns into the medium from which it originated. (Albregtsen, 2008) Snell’s Law states that the ratio of the sines of the angles of incidence and refraction of a wave is constant when it passes between two given media. (Oxford Dictionaries, 2018) “The angle (?) of incidence (i) = the angle (?) of reflection (r)”) (Physics Classroom, 2018) Unlike reflection, transmission is when the vibrations of the electrons in the light wave impinges on a transparent object and are passed on to neighbouring atoms through the material until it reaches the other side. Absorption of light occurs if the frequency of a light wave strikes a material with electrons having the same vibrational frequencies, causing those electrons to absorb the energy of the light wave and transform it into vibrational motion. During its vibration, the electrons interact with neighbouring atoms in a way in which converts the kinetic energy into thermal energy. (Henderson, 2007) Light consists have different wavelengths, each with a different frequency. (Waikato, 2012) The frequency of a wavelength determines its colour. The colour of an object is not contained within it but instead, it is the result of a light wave striking an object and becomes reflected by it, which is what is perceived by the human eye.
(Henderson, 2007)
