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  2. Light - Wikipedia

    en.wikipedia.org/wiki/Light

    Light exerts physical pressure on objects in its path, a phenomenon which can be deduced by Maxwell's equations, but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c, the speed of light.

  3. List of physical quantities - Wikipedia

    en.wikipedia.org/wiki/List_of_physical_quantities

    Amount of substance: n: The quantity proportional to the number of particles in a sample, with the Avogadro constant as the proportionality constant: mole (mol) N: extensive, scalar Luminous intensity: I v: Wavelength-weighted power of emitted light per unit solid angle: candela (cd) J: scalar

  4. Luminous energy - Wikipedia

    en.wikipedia.org/wiki/Luminous_energy

    This is sometimes called the quantity of light. [1] Luminous energy is not the same as radiant energy , the corresponding objective physical quantity . This is because the human eye can only see light in the visible spectrum and has different sensitivities to light of different wavelengths within the spectrum.

  5. Energy - Wikipedia

    en.wikipedia.org/wiki/Energy

    Energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light.

  6. Photon - Wikipedia

    en.wikipedia.org/wiki/Photon

    A photon (from Ancient Greek φῶς, φωτός (phôs, phōtós) 'light') is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force.

  7. Physical property - Wikipedia

    en.wikipedia.org/wiki/Physical_property

    A physical property is any property of a physical system that is measurable. [1] The changes in the physical properties of a system can be used to describe its changes between momentary states. A quantifiable physical property is called physical quantity. Measurable physical quantities are often referred to as observables.

  8. Physical quantity - Wikipedia

    en.wikipedia.org/wiki/Physical_quantity

    A physical quantity can be expressed as a value, which is the algebraic multiplication of a numerical value and a unit of measurement. For example, the physical quantity mass, symbol m, can be quantified as m=n kg, where n is the numerical value and kg is the unit symbol (for kilogram). Quantities that are vectors have, besides numerical value ...

  9. Luminous intensity - Wikipedia

    en.wikipedia.org/wiki/Luminous_intensity

    The frequency of light used in the definition corresponds to a wavelength in a vacuum of 555 nm, which is near the peak of the eye's response to light. If the 1 candela source emitted uniformly in all directions, the total radiant flux would be about 18.40 mW , since there are 4 π steradians in a sphere.