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The Photon theory is a core concept in quantum physics and understanding it is essential. Wave theory says light travels as waves (electromagnetic or mechanical). The photon theory is specifically the particle description of light as discrete energy packets. The photon theory states that light energy is not continuous but travels in discrete packets called photons or quanta. Each photon has energy E = hf where h is Planck's constant (6.626 × 10⁻³⁴ J·s) and f is the frequency. Photons have zero rest mass travel at speed of light and carry momentum p = h/λ. This theory was developed by Einstein in 1905 building on Planck's quantum hypothesis of 1900. Light is a TRANSVERSE wave not longitudinal. Longitudinal waves (like sound) have compressions and rarefactions. The transverse nature of light is proved by polarization which is only possible in transverse waves. Light is an electromagnetic wave and does NOT need a medium. It can travel through vacuum unlike mechanical waves like sound.
FAQ
Common questions and clear answers for this topic.
Optics is the branch of physics that studies the behavior of light, including its reflection, refraction, and interaction with lenses and mirrors.
Reflection is the bouncing back of light when it strikes a surface, while refraction is the bending of light as it passes from one medium to another with a different optical density.
A lens is a transparent optical device with curved surfaces that refracts light to converge or diverge rays, commonly classified as convex (converging) or concave (diverging).
The speed of light in a vacuum is approximately 3 x 10^8 meters per second, denoted by the symbol c.
Total internal reflection occurs when light traveling from a denser medium to a rarer medium strikes the boundary at an angle greater than the critical angle, causing it to be completely reflected back into the denser medium.
