Absorption Definition Physics
According to physics, absorption of electromagnetic radiation is considered as a process that shows how a matter can take up a photon's energy and then transform electromagnetic energy into internal energy of the absorber. One example of such an absorber is thermal energy. The absorption of waves never depends on the intensity of the matter. According to wave motion, absorption is considered as the transfer of energy of a wave to a matter; this happens when the wave passes through the matter.
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Absorb Physics
Absorb definition physics is a phenomenon that happens when a wave comes in contact with a medium and forces the molecules of the medium to vibrate, move and change their places. Some of the energy of the wave gets reduced during this process because the vibration takes away some of the wave's energy. As there is minimal energy present in the wave, therefore less of the energy gets reflected.
Let's discuss one example of absorption. Black pavement can be considered as one of the examples because black pavement absorbs energy from light. The black pavement usually becomes hot instantly because it absorbs most of the light waves that reflect on it, and a little of the light waves are reflected back; thus, the pavement appears black. If you draw a white line on the black pavement, then it will reflect more because the white colour doesn't absorb more light waves. So, the white strip drawn by you will be less hot as compared to other surfaces that are painted black.
Absorption in Laser Physics
According to researchers, the laser can get easily absorbed inside an optical substrate by using several methods which are distinct from each other. Electrons that are present in the discrete energy tend to level up the atoms that forced the optical medium to absorb radiative photons and are pushed to the semi-table, higher energy levels.
These atoms, after this phenomenon, start to fluoresce and begin to emit radiation in the form of photons through spontaneous emission when electrons start falling back to a lower energy level.
Unintentional fluorescence is the reason for loss of energy and also acts as a barrier in signal detection, which is considered detrimental in the case of laser optics applications. Most of the time, fluorescence is isotropic and tends to radiate in every direction, which makes things worse than before. The main cause of fluorescence is the impurities that are present in the substrate, for example, rare-earth ions.
For example, UV grade fused silica is a substance that can explain high transmittance in the UV and visible spectra. Still, they experience dips in transmittance, which are centred at 1.4um, 2.2um, and 2.7um due to absorption from Hydroxide ion impurities. On the other hand, IR grade fused silica is known for having a lower amount of hydroxide ions; this immediately results in greater transmission throughout the NIR spectrum.
The above explanation and example can make you understand what absorption is and how it operates using a laser.
Absorption Spectrum Definition Physics
The absorption spectrum is defined as an electromagnetic spectrum within which a decrease in the intensity of radiation at particular wavelengths or various wavelengths characteristic of a specific absorbing substance gets manifested in the form of dark lines or bands.
An absorption spectrum generates when a light goes through a cold, dilute gas. Atoms that are present in the gas starting absorbing in different frequencies. Since the light which got re-emitted is unlikely to get emitted in the same direction as one of the absorbed photons, this phenomenon is the reason for dark lines getting created in the spectrum.
An absorption spectrum gets created from the frequencies of light that are transmitted through dark bands when energy gets absorbed with the help of electrons at the time when they are present in the ground state to reach high energy states.
This is what you will learn from the absorption spectrum. It isn't easy, but regular practice can help you achieve perfection in this particular topic.
FAQs on Absorption
1. What is meant by absorption in Physics?
In Physics, absorption is a physical or chemical process where atoms, molecules, or ions enter into a bulk phase—be it a gas, liquid, or solid material. It is the phenomenon by which a substance captures and transforms energy. For instance, when light hits an object, some of its energy is absorbed and often converted into heat. This is distinct from transmission (energy passing through) and reflection (energy bouncing off).
2. What is the fundamental difference between absorption and adsorption?
The primary difference lies in where the process occurs. Absorption is a bulk phenomenon, meaning the substance being absorbed is distributed throughout the entire volume of the material. In contrast, adsorption is a surface phenomenon, where particles adhere only to the surface of the other substance. A simple analogy is a sponge absorbing water (bulk) versus dust settling on a table (surface). For a deeper dive, you can explore the difference between absorption and adsorption in more detail.
3. How does an absorption spectrum differ from an emission spectrum?
An absorption spectrum and an emission spectrum are essentially opposites and provide information about a substance's atomic structure. The key differences are:
- Formation: An absorption spectrum is created when atoms absorb specific frequencies of light, causing an electron to jump to a higher energy level. An emission spectrum is produced when excited atoms release energy as their electrons fall to lower energy levels.
- Appearance: An absorption spectrum appears as a continuous spectrum (like a rainbow) with specific dark lines where light has been absorbed. An emission spectrum consists of bright coloured lines on a dark background, corresponding to the specific frequencies of light emitted.
- Energy Process: Absorption is an energy-gaining process for the atom, while emission is an energy-releasing process.
You can learn more about the difference between emission and absorption spectra to understand atomic physics better.
4. Can you provide some real-world examples of absorption from a Physics perspective?
Certainly. Absorption is a common phenomenon we encounter daily. Here are a few examples:
- Heat Absorption: A dark-coloured car parked in the sun absorbs more sunlight and gets hotter inside compared to a light-coloured car, which reflects more sunlight.
- Light Absorption: Plants use chlorophyll to absorb specific wavelengths of sunlight to perform photosynthesis. Sunglasses work by absorbing a portion of the UV and visible light, protecting our eyes.
- Sound Absorption: Soft, porous materials like foam panels or heavy curtains are used in studios and theatres to absorb sound waves, preventing echoes and reducing noise levels.
5. Why do dark-coloured objects heat up more in the sun than light-coloured ones?
This happens because of their different abilities to absorb and reflect light. Dark-coloured objects, especially black ones, absorb most of the wavelengths of light that fall on them. This absorbed light energy is converted into thermal energy (heat), causing the object's temperature to rise significantly. In contrast, light-coloured objects reflect most of the light wavelengths. Since less energy is absorbed, less is converted to heat, and the object remains cooler. A perfect black body is an ideal absorber of all radiation.
6. What is the physical process behind the absorption of light by a material?
The absorption of light is fundamentally an atomic or molecular process governed by quantum mechanics. When a photon of light strikes an atom, it can be absorbed only if its energy precisely matches the energy difference between the atom's current electron energy level (ground state) and a higher, unoccupied energy level. If the energy matches, the electron absorbs the photon and 'jumps' to the higher energy level. This process removes that specific frequency of light from what is transmitted or reflected. The excited electron will later return to a lower state, often releasing the energy as heat or light of a different frequency (fluorescence). You can read more about the emission and absorption of light in Bohr's atom model.
7. How is the absorption of sound different from the absorption of light?
While both involve the loss of energy, the mechanisms are very different. Sound absorption is a mechanical process. Sound waves cause particles of a medium (like air) to vibrate. When these waves hit a porous material, the vibrations cause friction between the air molecules and the material's fibres, converting the sound energy into a small amount of heat. In contrast, light absorption is an electromagnetic process where the energy of a photon is transferred to an electron, causing it to change its energy state. Therefore, sound absorption depends on material properties like porosity and density, while light absorption depends on the electronic structure of atoms.
8. What does the absorption coefficient of a material signify in Physics?
The absorption coefficient is a quantitative measure of how effectively a material absorbs energy, particularly light, as it passes through it. It signifies the rate at which the intensity of radiation decreases per unit distance inside the material. A material with a high absorption coefficient will absorb energy very quickly over a short distance, making it opaque. Conversely, a material with a low absorption coefficient is more transparent because light can travel further through it before being absorbed. This property is crucial in fields like optics and material science and is a key component of the Beer-Lambert Law, which relates absorption to the concentration of a substance.
