2A3 Absorption and Emission Flashcards
Explain electronic transitions and electromagnetic radiation, including their relationship to absorption and emission spectra.
Define:
electromagnetic radiation
A wave propagating through space, carrying energy at the speed of light.
It consists of oscillating electric and magnetic fields.
Electromagnetic radiation travels at the speed of light since it does not require a medium to travel.
How does light behave according to quantum theory?
It behaves as both a particle and a wave.
This dual nature is central to quantum mechanics.
What is the electromagnetic spectrum?
The range of all types of electromagnetic radiation.
It includes all seven types of light listed from the lowest to the highest frequency.
List seven types of electromagnetic waves in order of decreasing wavelengths.
- Radio waves
- Microwaves
- Infrared light
- Visible light
- Ultraviolet light
- X-rays
- Gamma rays
Gamma rays have the shortest wavelength and highest frequency, while radio waves have the longest wavelengths and shortest frequency.
What is the visible spectrum range?
400 to 700 nm
It spans from violet (shorter wavelength) to red (longer wavelength) light.
The frequency range of visible ranges from 400 to 750 trillion Hertz.
What are radio waves characterized by?
- Low frequency
- Long wavelength
Wavelength above 1 millimeter.
Frequency below 300 billion Hz.
List four uses of microwaves.
- Microwave ovens
- Radar
- GPS
- Wi-Fi
They have wavelengths between 1 millimeter and 25 micrometers.
Fill in the blank:
The energy of light is directly proportional to __________?
frequency
Energy increases with an increase in frequency, according to the energy equation where E=hc/λ. Gamma rays are high frequency and are therefore contain huge amounts of energy.
Fill in the blanks:
Infrared light is defined as having wavelengths between _______ and _________ micrometers.
25; 2.5
Infrared means ‘below red’ in Latin.
Fill in the blanks:
Ultraviolet light wavelengths range from ______ to _______ nanometers.
1; 400
Ultraviolet light can cause sunburns.
Which types of electromagnetic waves are generally harmless to humans?
- Radio waves
- Microwaves
- Infrared light
- Visible light
These have low frequencies and long wavelengths.
High-frequency waves like ultraviolet light, X-rays, and gamma rays strip electrons from materials and damage human cells.
Explain why X-rays have higher energy than visible light.
- Higher frequencies
- Shorter wavelengths
Higher-frequency waves carry more energy.
X-rays are capable of damaging human cells but are useful in medical diagnostics with proper protection.
What is a wave?
A propagating and oscillating deformation of some quanta or medium.
Waves can take various forms such as water, sound, and electromagnetic waves.
List five parameters used to describe waves.
- Amplitude
- Frequency
- Wavelength
- Speed
- Period
These characteristics help quantify and understand wave behavior.
Define:
wavelength
The distance between two consecutive peaks or troughs of a wave.
This value is often measured in meters or nanometers.
Define:
frequency
The number of completed wave cycles in a given period of time.
It is measured in hertz (Hz), where 1 Hz equals 1 wave per second or 60 revolutions per minute.
A frequency of 15 Hz indicates 15 wave cycles per second.
Frequency (ν) is given by the formula ν = 1/T, where T is the period of the wave.
What is the relationship between frequency and wavelength?
The two are inversely proportional.
Higher frequency results in shorter wavelengths while lower frequency results in longer wavelengths.
The relationship is described by the formula λ = c /ν, where λ is the wavelength, c is the speed of light, and ν is the frequency.
Define:
period
The amount of time it takes to complete a wave cycle.
Periods can be calculated by taking the inverse of the frequency, which means dividing 1 by the frequency value.
What is the formula for calculating the wavelength (λ) of light?
λ = v / f
v refers to the speed of light, and f is the frequency of the wave. When calculating the wavelength of other kinds of waves, v will refer to the wave speed, not the speed of light.
Define:
amplitude
The distance from the midline of a wave to its crest or trough.
Amplitude also measures the amount of energy transported by the wave.
Higher amplitude means more energy carried by the mechanical and electronegative waves.
It is measured in meters for transverse waves and in units of pressure for longitudinal waves.
What is the difference between amplitude and frequency?
Amplitude measures energy, while frequency measures how often waves occur.
Two waves can have the same frequency but different amplitudes.
What is emitted when an electron transitions from a higher energy level to a lower energy level?
A photon
It can be defined as a quantum of electromagnetic radiation, representing a particle of light.
The emitted photon varies in frequency and can be in the range of ultraviolet, visible, or infrared light.
What is the relationship between energy and frequency of a photon?
Energy is directly proportional to frequency.
Higher-frequency photons have more energy.
This is described by Planck’s equation, E=hν, where E is the energy, ν is the frequency, and h is Planck’s constant.
What is the energy of a photon with a frequency of 5×10^14 Hz?
3.31×10^-19 J
Using E=hν, where h=6.626×10^-34 J and ν = 5×10^14 Hz.
Fill in the blank.
The photoelectric effect involves the emission of ___________ from a metal surface.
electrons
Electrons are emitted when light of sufficient energy strikes a metal surface.
How does the photoelectric effect support the particle nature of light?
Light ejects electrons from a material only if its frequency is above a threshold.
This demonstrates that light is quantized into photons.
Photon quantization implies that light is emitted or absorbed in discrete packets called photons.
What is the relationship between energy quantization and electron transitions?
Energy is quantized, meaning electrons can only occupy specific allowed energy levels.
This quantization restricts the energies that can be absorbed or emitted.
What type of spectrum is produced by electronic transitions?
Line spectrum
Each element’s spectrum is unique due to specific energy level differences.
What happens to electrons when an atom absorbs energy?
Electrons become excited and move to higher energy orbitals.
Excited electrons carry more energy and oscillate quicker than ground state electrons.
What determines the color of light emitted by an atom?
The energy difference between two electronic levels.
Larger energy gaps produce shorter wavelengths.
The specific wavelengths correspond to different colors in the visible spectrum.
Explain why visible spectra are limited to certain colors.
Only specific wavelengths correspond to energy differences in visible transitions.
Visible transitions occur in the range of 400 to 700 nm.
What is the significance of temperature and pressure in electronic transitions?
They affect energy changes within an atom.
Due to this, experiments should be conducted at sea level and room temperature unless otherwise specified.
How do spectral lines correlate with electronic transitions?
Each line corresponds to a specific transition between energy levels.
Lines indicate emitted or absorbed photons.
List three series named after physicists that describe electronic transitions in hydrogen.
- Lyman series that correspond to transitions ending at n=1.
- Balmer series that correspond to transitions ending at n=2.
- Paschen series that correspond to transitions ending at n=3.
Lyman transitions occur in the ultraviolet region.
Balmer transitions occur in the visible region.
Paschen transitions occur in the infrared region.
Fill in the blank:
Higher energy transitions correspond to ___________ wavelengths.
shorter
Energy and wavelength are inversely proportional.
Define:
spectroscopy
The process of identifying a compound by its electron emission spectrum.
It involves analyzing atomic spectra.
This relies on the specific colors of light emitted when electrons return to ground state.
Spectroscopy applies spectrometers to measure spectral lines to determine chemical composition.
True or False:
All elements produce the same spectral lines.
False
Each element has unique spectral lines due to specific energy levels.
The unique spectral lines act as fingerprints for elements allowing atomic identification.
