Emission and Absorption Spectra

Bozeman Science
6 Mar 201505:18
EducationalLearning
32 Likes 10 Comments

TLDRIn this AP Physics essentials video, Mr. Andersen explores the concepts of emission and absorption spectra. He explains how hydrogen gas, when excited in a discharge chamber, emits discrete units of light corresponding to specific energy levels. This emission spectrum can be analyzed using a prism, revealing the unique colors associated with each energy transition. Conversely, when light is shone through the gas, some wavelengths are absorbed, creating an absorption spectrum. Bohr's model of the atom helps explain these phenomena, where electrons absorb or emit photons as they transition between energy levels. The video also discusses the broader spectrum, including infrared and ultraviolet light, and illustrates how different elements produce distinct spectral lines, which are crucial for identifying the composition of substances.

Takeaways
  • 🌟 Emission and absorption spectra are key concepts in understanding atomic behavior. When a gas like hydrogen is excited by electrons in a discharge chamber, it emits light with discrete wavelengths, creating an emission spectrum.
  • 🔬 The discrete units of light observed in the emission spectrum are due to the quantized energy levels of the hydrogen atom. Electrons can only transition between these levels, emitting or absorbing photons with specific energies.
  • 🌈 When analyzing light through a prism, the light is split into its constituent colors, demonstrating the spectrum of visible light. However, there are also invisible parts of the spectrum, such as infrared and ultraviolet light.
  • 💡 Niels Bohr's model of the atom explains the emission and absorption spectra. Electrons in a hydrogen atom jump between energy levels, emitting or absorbing photons with energy corresponding to the difference between those levels.
  • 🚫 Only photons with the correct energy can cause an electron to transition to a higher energy level. If the photon's energy does not match the energy difference between levels, it will not be absorbed.
  • 🔄 Conservation of energy is fundamental in both absorption and emission processes. The energy of the photon and the atom before absorption equals the energy inside the atom after absorption, and similarly for emission.
  • 🔍 Scientists can identify elements and molecules by analyzing their emission spectra. Each element has a unique set of energy levels, resulting in a distinctive pattern of spectral lines.
  • 🌌 The visible light spectrum is just a small part of the full electromagnetic spectrum. Beyond visible light, there are infrared and ultraviolet regions, each with its own applications and properties.
  • 💥 In the video's simulation, a continuous stream of electrons hitting hydrogen atoms results in the emission of photons of various colors, demonstrating how different energy transitions produce different wavelengths of light.
  • 🌈 The simulation also shows how different atoms, such as mercury or neon, have different energy levels and thus produce different spectral lines, leading to their characteristic colors when used in lights.
  • 📊 A spectrogram can visually represent the spectral lines, showing the specific wavelengths emitted or absorbed by an atom, which is crucial for identifying the composition of celestial bodies or chemical substances.
Q & A

  • What happens when a gas like hydrogen is placed in a discharge chamber and electrons are shot at it?

    -The gas will give off light that can be analyzed and split into discrete units of light, or photons, carrying discrete amounts of energy when passed through a prism.

  • What is the significance of the discrete units of light observed in the emission spectrum of hydrogen?

    -The discrete units of light indicate specific energy levels that electrons can occupy in a hydrogen atom, and they are the result of electrons transitioning between these levels.

  • What is an absorption spectrum and how does it differ from an emission spectrum?

    -An absorption spectrum is the result of shining light through a medium where certain parts of the light are absorbed, unlike an emission spectrum where light is emitted by atoms or molecules as they transition between energy levels.

  • Who is credited with the explanation of the emission and absorption spectra of hydrogen?

    -Niels Bohr is credited with providing the explanation for the emission and absorption spectra of hydrogen, relating them to electron transitions between energy levels.

  • How does the energy conservation principle apply to the absorption and emission of light by atoms?

    -According to the energy conservation principle, the amount of energy in the photon and the atom or nucleus before absorption is equal to the amount of energy inside the atom or nucleus after absorption. Similarly, the energy in the atom or nucleus before emission is equal to the energy of the emitted photon plus the energy of the atom or nucleus after emission.

  • Why is the study of emission and absorption spectra valuable in science?

    -The study of emission and absorption spectra is valuable because it allows scientists to identify the elements and molecules present in a sample by analyzing the specific wavelengths of light that are emitted or absorbed, which correspond to the energy levels of the electrons in those substances.

  • What is the relationship between visible light and the spectrum of light that is produced when it passes through a prism?

    -Visible light encompasses all the colors of the spectrum, which are produced when white light passes through a prism and is split into its constituent wavelengths. This visible spectrum is flanked by infrared and ultraviolet light, which are not visible to the human eye.

  • What happens to an electron in a hydrogen atom when it absorbs a photon of the correct color?

    -When an electron in a hydrogen atom absorbs a photon of the correct color, it gains energy and jumps to a higher energy level.

  • How does the color of light emitted by an electron relate to the energy level transition it undergoes?

    -The color of light emitted by an electron is directly related to the energy level transition it undergoes. When an electron falls from a higher energy level to a lower one, it emits a photon of light with a color corresponding to the energy difference between those levels.

  • What is a PHET simulation and how is it used in the context of the script?

    -A PHET simulation is an interactive computer model used for education, often to visualize and explore scientific concepts. In the context of the script, a PHET simulation is used to demonstrate the emission of light from a hydrogen atom when it is excited by a stream of electrons.

  • How do different gases, like mercury or neon, produce different colors in a gas discharge tube?

    -Different gases have different electron energy levels, which result in different colors of light being emitted when the electrons transition between these levels. For example, neon gas emits a reddish color due to the specific energy levels of its electrons and the corresponding photons emitted during transitions.

Outlines
00:00
🌟 Emission and Absorption Spectra in Physics

Mr. Andersen introduces the concept of emission and absorption spectra in the context of atomic physics. He explains that when hydrogen gas is placed in a discharge chamber and bombarded with electrons, it emits light that, when passed through a prism, reveals discrete units of light corresponding to specific energy levels. This phenomenon was historically puzzling until Niels Bohr's quantum theory provided an explanation. The video also discusses how shining light through a discharge chamber results in an absorption spectrum, where certain colors of light are absorbed by the gas. The conservation of energy is highlighted as a fundamental principle in these processes, with the energy of the photon being equal to the energy change within the atom during absorption or emission. This understanding is crucial for analyzing the composition of elements and molecules based on their unique spectral signatures.

Mindmap
Keywords
💡Emission and Absorption Spectra
Emission and absorption spectra are two types of spectra that describe how light interacts with matter. Emission spectra occur when atoms or molecules emit light at specific wavelengths as electrons transition between energy levels. Absorption spectra happen when atoms or molecules absorb light of specific wavelengths, causing electrons to move to higher energy levels. In the video, Mr. Andersen demonstrates how hydrogen gas in a discharge chamber emits light at discrete wavelengths, creating an emission spectrum, and how some light is absorbed, creating an absorption spectrum.
💡Discrete Units of Light
Discrete units of light refer to individual packets of energy carried by photons, which correspond to specific wavelengths of light. The concept is central to the video as it explains that when hydrogen gas is excited, it emits light not as a continuous spectrum but in discrete units, each with a particular energy. This is a key aspect of quantum mechanics and is illustrated by the prism splitting the light into distinct lines, each representing a different energy level transition within the hydrogen atom.
💡Niels Bohr
Niels Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, particularly through his Bohr model of the atom. In the context of the video, Bohr's model explains how electrons in atoms can only occupy certain energy levels and that light is emitted or absorbed in discrete amounts when electrons transition between these levels. His work was pivotal in solving the puzzle of why atoms absorb and emit light at specific wavelengths.
💡Conservation of Energy
The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. In the video, this principle is applied to atomic and nuclear processes, where the energy of a photon before absorption by an atom is equal to the energy of the atom after absorption. Similarly, when an electron drops from a higher to a lower energy level, the energy of the emitted photon equals the energy difference between the levels. This conservation is fundamental to understanding emission and absorption spectra.
💡Energy Levels
Energy levels in the context of the video refer to the specific, quantized states of energy that electrons in atoms can occupy. These levels are discrete and defined by quantum mechanics. When electrons transition between these levels, they either emit or absorb photons with energy corresponding to the difference between the levels. The video uses the hydrogen atom as an example, showing that when electrons move from one energy level to another, they emit or absorb light of specific colors or wavelengths.
💡Spectrogram
A spectrogram is a visual representation of spectra, typically used to depict the intensity of light as a function of both wavelength and time. In the video, Mr. Andersen uses a spectrogram to show how a continuous stream of electrons hitting hydrogen atoms results in a spectrum with multiple spectral lines, each corresponding to a specific electron transition. This tool helps visualize the discrete nature of the light emitted by atoms, which is a key feature of emission spectra.
💡Infrared and Ultraviolet Light
Infrared and ultraviolet light are parts of the electromagnetic spectrum that are adjacent to the visible light spectrum but are not visible to the human eye. Infrared light has longer wavelengths than visible red light, while ultraviolet light has shorter wavelengths than visible violet light. The video mentions these types of light to illustrate that the visible spectrum is just a small part of the full range of light that atoms can emit or absorb, and that different atoms can emit light in these non-visible regions as well.
💡PHET Simulation
A PHET simulation, developed at the University of Colorado Boulder, is an interactive, research-based simulation used to teach science and mathematics concepts. In the video, Mr. Andersen uses a PHET simulation to demonstrate the emission of light from a hydrogen atom when it is excited by a stream of electrons. This simulation allows viewers to see how atoms can be bombarded with electrons and emit light at specific wavelengths, which is a practical application of the principles discussed in the video.
💡Electron Transitions
Electron transitions refer to the movement of electrons from one energy level to another within an atom. These transitions are integral to the discussion in the video as they are the mechanism by which atoms emit or absorb light. When an electron transitions to a lower energy level, it emits a photon, and when it transitions to a higher level, it absorbs a photon. The specific color or wavelength of the photon is determined by the energy difference between the levels, which is why emission and absorption spectra are unique to each element.
💡Sodium and Neon
Sodium and neon are elements that, when excited, emit light at specific wavelengths that correspond to their unique electron energy levels. In the video, Mr. Andersen contrasts the hydrogen spectrum with those of sodium and neon to demonstrate how different elements have different energy level structures, resulting in distinct emission spectra. Sodium is known for producing a yellow light, while neon is known for its reddish glow, as seen in neon lights, due to the specific wavelengths of light emitted during electron transitions.
💡Quantum Mechanics
Quantum mechanics is a fundamental theory in physics that describes the behavior of matter and energy at very small scales, typically at the atomic and subatomic level. The video touches on quantum mechanics when discussing the discrete nature of energy levels and electron transitions within atoms. Quantum mechanics is essential for understanding the phenomena of emission and absorption spectra, as it provides the theoretical framework for why atoms can only absorb or emit light at certain, discrete wavelengths.
Highlights

Emission and absorption spectra are discussed in the video.

Hydrogen gas in a discharge chamber emits light when electrons are shot at it.

Light emitted from hydrogen can be analyzed through a prism to show discrete units of light.

Absorption spectra occur when light is shone through a discharge chamber and some is absorbed.

Niels Bohr's theory explains the emission and absorption of light by hydrogen atoms.

Electrons emit photons when they jump to lower energy levels.

Electrons absorb photons to move to higher energy levels.

Only discrete colors of light are required for electron transitions.

Conservation of energy is observed in both absorption and emission of light.

Emission spectra can reveal the elements present in a substance by analyzing the light given off.

Visible light is part of the spectrum, with infrared and ultraviolet light outside the visible range.

Energy level diagrams for hydrogen atoms show how specific colors of photons affect electron transitions.

Different atoms, such as mercury and neon, have unique emission spectra.

Sodium and neon gases emit specific colors of light due to their atomic structure.

Neon lights produce a reddish color from the sum of photons emitted by neon gas.

Understanding emission and absorption spectra helps in identifying elements and their energy transitions.

Transcripts

Browse More Related Video

Stimulated Emission

Light Absorption, Reflection, and Transmission

Wave Model of an Electron

Why do we see colour? Video

Applied Chemistry_ Hydrogen Spectrum_ Lecture 04 for Polytechnic 1st Semester

Atomic Energy Levels (Micro Lesson for AP Physics)

Rate This

5.0 / 5 (0 votes)

Thanks for rating:

Related Tags
Emission SpectraAbsorption SpectraHydrogen GasEnergy LevelsNiels BohrPhoton EnergyConservation of EnergySpectral AnalysisElement IdentificationPhysics Education