There are three modes of heat transfer: thermal conduction, convection and radiation. Thermal conduction is the movement of heat from one substance to another that has a different temperature when touching. As the temperature increases, the vibrational motion of the particles increases.
Since the particles in a solid are closely packed, the vibrating particles collide with the surrounding particles which transfers heat and vibrational energy, thus the reason why metal is a good thermal conductor.8 The electrons can leave their atoms in metal, so as the vibrational and heat energy increase in the hot particles, a portion of that energy is transferred to the free electrons that collide with cooler ions as they move through the structure of the metal. As the electrons collide with the cooler ions, it transfers some of its heat energy, thus making metal a good conductor due to how quick the electrons transfer heat.2 Thermal insulation, on the other hand, occurs when a barrier between the hot and cold object reduces heat transfer by either decreasing thermal conduction and convection (when hot air rises and cool air falls)3 or by reflecting thermal radiation.7 Radiation is the process of moving heat from one place to another without using a medium (particles in a solid, liquid or gas) and can travel in a vacuum (space).4 The sun transfers its light and heat energy through radiation (light and heat radiation). As the sun’s pure light, or white light, hits and object, it can either be absorbed, transmitted or reflected.
When white light hits a surface with the same natural frequencies, it will be absorbed and reemitted as heat energy.6 However, whatever colour/s that are in the white light are not absorbed, then the object will appear as that colour. Transmission occurs when the frequencies of the light wave does not match the natural frequencies of vibration of the object/s. Instead, when light wave strikes an object, the electrons in the atoms begin vibrating for brief periods of time with small amplitudes of vibrations instead of vibrating in resonance at a large amplitude. When an object or substance is transparent, then the vibrations of the electrons are passed on to neighbouring atoms through the bulk of the material and is reemitted on the opposite side of the object. Reflection, on the other hand, occurs when the object is opaque.
When the light wave hits the object, the electrons of the atom on the material’s surface vibrate for short periods of time and then reemit the energy as a reflected wave but it has less kinetic and heat energy.5 The angle of reflection can be calculated through Snell’s Law: the angle of incidence (i) = the angle of reflection (r).1 For this experiment, the group is going to discover what angle best reflects light to heat the pizza box through the knowledge of Snell’s Law.
