Laser Fundamentals Quiz

Laser stands for Light Amplification by Stimulated Emission of Radiation.

Lasers were invented and developed between 1959 and 1962.

Ordinary light is incoherent, while laser light is coherent.

<p>The three types are absorption, spontaneous emission, and stimulated emission.</p> Signup and view all the answers

<p>Induced absorption occurs when an atom in a lower energy state absorbs a photon and transitions to a higher energy state.</p> Signup and view all the answers

<p>Stimulated emission triggers an excited atom to drop to a lower energy state while releasing a photon.</p> Signup and view all the answers

<p>Lasers produce light of a single wavelength, making them monochromatic.</p> Signup and view all the answers

<p>Laser light is produced by stimulated emission, while ordinary light is generated by spontaneous emission.</p> Signup and view all the answers

<p>The lifetime of the excited state of an atom is approximately $10^{-8}$ seconds, which signifies how long an atom can remain in an excited state before returning to a lower energy state.</p> Signup and view all the answers

<p>Spontaneous emission occurs when an excited atom returns to a lower energy state without external influence, releasing energy as a photon.</p> Signup and view all the answers

<p>Spontaneous emission occurs naturally at the end of an atom's lifetime, while stimulated emission is initiated artificially before the end of the atom's lifetime.</p> Signup and view all the answers

<p>Stimulated emission occurs when an external photon triggers an excited atom to emit a photon, resulting in two coherent photons, while spontaneous emission occurs naturally without external photons.</p> Signup and view all the answers

<p>Spontaneous emission results in less intense and incoherent radiation, whereas stimulated emission yields highly intense and coherent radiation.</p> Signup and view all the answers

<p>This equation represents the process of stimulated emission where one photon interacts with an excited atom to produce two photons.</p> Signup and view all the answers

<p>In spontaneous emission, the excess energy from the transition of an atom from a higher energy state to a lower one is released as a photon.</p> Signup and view all the answers

<p>Light from spontaneous emission has less directionality and more angular spread, while light from stimulated emission is highly directional with less angular spread.</p> Signup and view all the answers

<p>Metastable states are excited states with longer lifetimes that allow the accumulation of excited atoms, which is crucial for achieving population inversion in lasers.</p> Signup and view all the answers

<p>External photons provide the necessary energy to trigger an excited atom's transition to a lower energy state, resulting in the emission of two coherent photons.</p> Signup and view all the answers

<p>Coherent light refers to light waves that are in phase and have a consistent frequency, produced as a result of the stimulated emission process.</p> Signup and view all the answers

<p>Radiative transitions involve the absorption or emission of radiation, while non-radiative transitions occur without such emission or absorption, primarily involving energy exchange with surroundings.</p> Signup and view all the answers

<p>The excited state is deemed highly unstable due to the atom's tendency to return to a lower energy state to achieve minimum potential energy.</p> Signup and view all the answers

<p>The probability of stimulated emission depends on both the properties of the energy states involved and the energy density of the incident radiation.</p> Signup and view all the answers

<p>Emitted light from stimulated emission is nearly monochromatic, while light from spontaneous emission is not monochromatic.</p> Signup and view all the answers

<p>Metastable states allow a larger number of atoms to remain excited for longer periods, enabling the necessary conditions for population inversion.</p> Signup and view all the answers

<p>Metastable states allow atoms to remain in an excited state for a longer time, facilitating stimulated emission and amplification in lasers.</p> Signup and view all the answers

<p>When a photon interacts with an excited atom, it stimulates the emission of another photon, leading to a doubling effect that amplifies light.</p> Signup and view all the answers

<p>Coherence refers to the consistent phase relationship among light waves; it's significant because it allows for the precise and focused nature of laser beams.</p> Signup and view all the answers

<p>Temporal coherence relates to the phase relationship of waves at different locations along the same propagation direction, while spatial coherence describes the phase relationship of waves traveling in perpendicular planes.</p> Signup and view all the answers

<p>Monochromaticity means that laser light is primarily of one wavelength; it's quantified by its high degree of purity but not absolute due to factors like Doppler effects.</p> Signup and view all the answers

<p>The avalanche effect refers to the rapid increase in the number of photons through successive stimulated emissions, crucial for creating a powerful laser beam.</p> Signup and view all the answers

<p>Weak perturbations and stimulating radiations can induce transitions from metastable states to lower energy states, enabling the process of stimulated emission.</p> Signup and view all the answers

<p>The process starts with one photon stimulating an excited atom, resulting in two photons, which interact with more excited atoms, creating an exponential chain reaction.</p> Signup and view all the answers

<p>Pumping raises atoms from lower energy levels to higher energy levels, creating a population inversion necessary for laser action.</p> Signup and view all the answers

<p>Optical pumping uses a light source to supply energy, often through short flashes, to excite atoms in the active medium.</p> Signup and view all the answers

<p>In electrical discharge, electrons are accelerated towards the anode, colliding with gas atoms to ionize them and induce population inversion.</p> Signup and view all the answers

<p>This involves excited atoms colliding inelastically with another type of atom to transfer energy and create population inversion.</p> Signup and view all the answers

<p>Chemical pumping derives energy from chemical reactions, such as the reaction between hydrogen and fluorine to generate heat for pumping.</p> Signup and view all the answers

<p>An active medium is a substance that, when excited, reaches population inversion and can promote stimulated emission of light.</p> Signup and view all the answers

<p>Direct conversion involves the transformation of electrical energy directly into radiant energy, as seen in light emitting diodes (LEDs).</p> Signup and view all the answers

<p>Electrical discharge is effective in gas lasers because it can ionize the medium and maintain low energy bandwidths.</p> Signup and view all the answers

<p>Population inversion is essential for laser operation as it ensures that the number of atoms in the excited state exceeds those in the ground state, allowing stimulated emission to dominate over spontaneous emission.</p> Signup and view all the answers

<p>The concept of negative temperature indicates a non-equilibrium state where the population of excited states exceeds that of lower energy states, mathematically represented as N2 &gt; N1.</p> Signup and view all the answers

<p>Pumping is the process of supplying energy to continuously promote atoms from a lower energy level to an excited state, ensuring a higher population in the excited state.</p> Signup and view all the answers

<p>Stimulated emission dominates over spontaneous emission when the photon energy, $hν$, is equal to or greater than the thermal energy, $kT$, and when the population of excited states exceeds that of lower energy states.</p> Signup and view all the answers

<p>When electromagnetic radiation is incident on a system at thermal equilibrium, net absorption occurs, as typical populations favor the ground state, N1 &gt; N2.</p> Signup and view all the answers

<p>Under normal conditions, population decreases with increasing energy level due to the tendency of systems to occupy lower energy states, following the Boltzmann distribution.</p> Signup and view all the answers

<p>An active system in the context of lasers refers to a system where population inversion is achieved and maintained, allowing for effective laser action.</p> Signup and view all the answers

<p>Laser light has a much narrower wavelength spread compared to normal sources because it results from stimulated emission, which produces coherent photons with identical energy and phase.</p> Signup and view all the answers