Wave Interference and Coherent Sources

Understanding Light as a Wave

• Photons have the right energies to cause chemical changes, and when UV light hits skin, it can cause chemical changes in DNA.
• UVB and UVC waves have more energy and greater potential to damage skin.

Photon and Sunburn

• UV light can cause chemical changes in skin cells, leading to sunburn.
• Photons have different energies, with UVB and UVC having more energy than visible light.

Photon Influence on Colors of Light

• The energy of each photon is directly related to the color of the light.
• A photon of red light has less energy than a photon of blue light.

Wave Nature of Light

• Thomas Young concluded that light behaves as a wave due to wave-interference phenomenon.
• Coherent sources of light are necessary for interference to occur, and monochromatic light is required for interference.
• Incoherent sources of light do not maintain a constant phase relationship with each other over time.

Wave Interference

• When two waves come close, their effects add together, resulting in constructive or destructive interference.
• Constructive interference occurs when crests of the waves align, resulting in a wave with greater amplitude.
• Destructive interference occurs when crests and troughs of the waves align, resulting in a wave with reduced amplitude.

Double Slit Experiment

• The double slit experiment demonstrates wave interference, with light passing through two slits and creating an interference pattern on a screen.
• The experiment shows that light behaves as a wave, with electrons also exhibiting wave-like behavior.

Propagation of Light

• Propagation of light refers to the transfer of energy from one point to another through electromagnetic waves.
• Light can travel through a medium without being reflected, absorbed, or scattered, resulting in 100% transmission.

Reflection and Refraction

• Reflection is the change in direction of a wavefront at an interface between two media, returning into the original medium.
• Refraction is the change in direction of a wave passing from one medium to another or through a gradual change in the medium.

Photon Concept

• A photon is the smallest discrete amount of electromagnetic radiation, and is the basic unit of all light.
• Photons have different energies, with red light having the least energy due to its lowest frequency.

Red Light in Photographic Dark Room

• Red light is used in photographic dark rooms because it does not overexpose or ruin pictures during the developing process.
• The arrangement of the visible spectrum of light shows that red color has the least frequency, which means it also has the least energy.