Electromagnetic Radiation Basics

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Questions and Answers

What type of electromagnetic radiation includes gamma rays and x-rays?

Nonionizing radiation

Infrared radiation

Ionizing radiation (correct)

Particulate radiation

Which of the following particles is not found in the nuclei of all atoms?

Positrons (correct)

Protons

Neutrons

Electrons

What is the significance of the equation E = mc² in the context of radiation?

It indicates the mass of photonic energy

It describes the relationship between mass and energy (correct)

It relates to the speed of sound in a medium

It defines the frequency of electromagnetic radiation

Which type of radiation is characterized by having insufficient energy to ionize atoms?

Nonionizing radiation Signup and view all the answers

Which type of ionizing radiation consists of two protons and two neutrons?

Alpha particles Signup and view all the answers

Which type of electromagnetic radiation has photons with the highest energy?

Gamma Rays Signup and view all the answers

What is the primary application of gamma rays in imaging?

To image the distribution of radiopharmaceuticals Signup and view all the answers

What does the energy of a photon depend on according to the formula E = hf?

The frequency of the wave Signup and view all the answers

Which characteristic distinguishes ionizing radiation from non-ionizing radiation?

Ionizing radiation can remove tightly bound electrons from atoms Signup and view all the answers

Which of the following electromagnetic radiations is used in computed tomography (CT) imaging?

X-rays Signup and view all the answers

Which of the following characteristics does electromagnetic radiation NOT possess?

Mass that can be affected by magnetic fields Signup and view all the answers

What is the wavelength range for gamma rays compared to visible light?

Shorter than visible light Signup and view all the answers

How is the energy of a photon related to its frequency?

Energy is directly proportional to frequency Signup and view all the answers

Which type of radiation is considered non-ionizing?

Radio waves Signup and view all the answers

What relationship holds true between speed, wavelength, and frequency for electromagnetic waves?

Speed remains constant while frequency and wavelength are variable Signup and view all the answers

Which of the following statements about electromagnetic radiation is false?

Electromagnetic radiation has mass. Signup and view all the answers

What does the phase constant (ϕ) in the sinusoidal wave function represent?

The starting point of the wave at t=0 Signup and view all the answers

In the sinusoidal wave function, what does the variable 'A' represent?

Amplitude of the wave Signup and view all the answers

What characteristic of electromagnetic waves allows them to change trajectory when interacting with matter?

Absorption Signup and view all the answers

What is the wavelength range of infrared waves?

About 10-3 m to 7×10-7 m Signup and view all the answers

Which electromagnetic waves are primarily used in radar systems?

Microwaves Signup and view all the answers

What is the main source of ultraviolet light that reaches the Earth?

The sun Signup and view all the answers

What is a common application of X-rays in medicine?

Bone fracture diagnosis Signup and view all the answers

Which type of electromagnetic radiation poses a high risk of damage to living tissue when absorbed?

Gamma Rays Signup and view all the answers

What type of particles are emitted during radioactive decay that are positively charged?

Positrons Signup and view all the answers

Which statement regarding electromagnetic radiation is false?

All types of EM radiation are capable of ionizing atoms. Signup and view all the answers

How is particulate radiation fundamentally different from electromagnetic radiation?

Particulate radiation involves mass, while electromagnetic radiation is massless. Signup and view all the answers

In the context of radiation, what does the equation E = mc² illustrate?

The conversion of mass into energy. Signup and view all the answers

Which type of radiation is characterized by being emitted from the nuclei of radioactive atoms?

Both B and C Signup and view all the answers

Which of the following describes the energy contribution of a photon?

Directly proportional to its frequency. Signup and view all the answers

What distinguishes alpha particles from beta particles in terms of composition?

Alpha particles consist of protons and neutrons; beta particles are electrons. Signup and view all the answers

Which characteristic is commonly associated with non-ionizing radiation compared to ionizing radiation?

Does not produce ionized atoms. Signup and view all the answers

Which statement accurately describes the composition of the atomic nucleus?

It consists of protons and neutrons. Signup and view all the answers

What is the maximum number of electrons that the L shell can hold?

8 Signup and view all the answers

Which type of nuclear family includes nuclides with the same atomic number but different mass numbers?

Isotopes Signup and view all the answers

What is the importance of the binding energy of an electron in an atom?

It is required to completely remove an electron from the atom. Signup and view all the answers

Which of the following statements is true regarding nuclear stability?

Heavy elements require a higher neutron-to-proton ratio for stability. Signup and view all the answers

What does the notation $^{A}_{Z}X$ represent in nuclear chemistry?

The mass number, atomic number, and chemical symbol. Signup and view all the answers

Which statement about electron orbits within the Bohr model is correct?

Electrons can only occupy certain discrete energy states. Signup and view all the answers

Study Notes

Electromagnetic (EM) Radiation

EM radiation includes visible light, radio waves, and X-rays
It has no mass and isn't affected by electric or magnetic fields
Travels at a constant speed in a given medium
Travels in straight lines, but its trajectory can be altered by interacting with matter
Absorption reduces radiation
Scattering changes radiation's trajectory

EM Wave Characteristics

EM waves are characterized by amplitude, wavelength (λ), frequency (f), and period (T)
Speed (v or c), wavelength, and frequency are related by λ=vT or v = λf
Wavelengths are typically measured in nanometers (10⁻⁹ m)
Frequencies are expressed in hertz (Hz) (1 Hz = 1 cycle/second =1 sec⁻¹)
For EM waves, v is the speed of light

Sinusoidal EM Wave

EM waves oscillate in electric and magnetic fields that are perpendicular to each other and to the direction of wave travel.
Wavelength (λ) is the distance between corresponding points on two consecutive waves.
Amplitude is the maximum displacement from the zero position along the direction of oscillation.
The electric and magnetic fields are 90° out of phase.

Sinusoidal Wave Function

The sinusoidal wave function can be written as y(x, t) = A sin(kx − ωt + φ), where:
- A is the amplitude
- k is the wave number (2π/λ)
- ω is the angular frequency (2πf)
- φ is the phase constant
It can also be expressed as a cosine function.
In 3D, x is replaced by the position vector (x, y, z).

The Spectrum of the EM Waves

Includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays
Types of waves often overlap
Distinguished by frequency or wavelength.
Specific wavelengths correlate to specific color/radiation types
There is a relationship between wavelength, frequency, and energy.
Different frequencies/wavelengths are used for different applications

Notes on the EM Spectrum

Radio waves have wavelengths greater than 10⁴ m to ~0.1 m. Used in radio & TV
Microwaves have wavelengths from ~0.3 m to 10⁻⁴ m. Useful for radar and ovens
Infrared wavelengths are ~10⁻³ m to 7 x 10⁻⁷ m. Produced by heat, readily absorbed by materials
Visible light is detected by the human eye. Most sensitive to ~ 5.5 x 10⁻⁷ m (yellow-green)
Ultraviolet light covers ~ 4 × 10⁻⁷ m to 6 × 10⁻¹⁰ m. Important radiation source from the sun and absorbed in the stratosphere by ozone
X-rays have wavelengths ~10⁻⁸ m to 10⁻¹² m. Produced by high-energy electrons, used in medicine (diagnostic / therapeutic).
Gamma rays have wavelengths ~10⁻¹⁰ m to 10⁻¹⁴ m. Emitted by radioactive nuclei, highly penetrating, and damaging. Used in medicine.

Particulate Radiation

Protons: Found in nuclei of all atoms, have a single positive charge
Electrons: Exist in atomic orbits, emitted from some radioactive atoms (beta particles ⁻)
Positrons: Positively charged electrons (β⁺), emitted by some nuclei during radioactive decay
Neutrons: Uncharged nuclear particles, released by nuclear fission and used for radionuclide production

Mass Energy Equivalence

Einstein's theory of relativity: Mass and energy are interchangeable
E = mc² (E representing energy, m representing mass, and c representing the speed of light)

Fundamental Properties of Particulate Radiation

Table including particles (proton, electron, positron, neutron), their symbols, relative charge in multiples of the electron charge, and approximate energy in MeV.

Structure of the Atom

Smallest division of an element with maintained chemical identity
Composed of a dense, positively charged nucleus containing protons and neutrons, with a cloud of negatively charged electrons outside the nucleus.
Electrically neutral in its nonionized state

Bohr Model of the Atom

Electrons orbit a dense, positively charged nucleus at fixed distances
Each electron occupies a discrete energy state in a given electron shell
Shells are assigned letters (K, L, M, N...) and quantum numbers (1, 2, 3, 4...)
Each shell can hold a maximum of (2n²) electrons, with n being the quantum number

Electron Shells

Diagram showing electron energy levels (K, L, M, N...) around the nucleus
Quantum number, maximum number of electron capacity

Binding Energy of Electron

Energy required to remove an electron completely from an atom
Conventionally negative and increases with closeness to the nucleus
Binding energy increases with the number of protons in the nucleus (atomic number)

Atomic Nucleus

Composed of protons and neutrons (collectively, nucleons)
The number of protons is the atomic number (Z)
The total number of protons and neutrons is the mass number (A)
Notation for an atom is ᴬₓ (with chemical symbol X)

Nuclear Energy Levels

Nuclei have energy levels analogous to electron shells
Lowest energy state is called the ground state
Nuclei with higher energy are in the excited state
Excited states that last longer than 10−¹² seconds are metastable, also called isomeric states, denoted by the letter m after the mass number (e.g., Tc-99m).

Nuclear Families

Table with categories (isotopes, isobars, isotones, and isomers) showing nuclides with similar properties
Examples for each family

Nuclear Stability

Only specific neutron-proton combinations are stable
Heavy elements require a higher neutron-to-proton ratio to offset electrostatic forces between protons
Nuclei with odd numbers of both neutrons and protons tend to be unstable

Nuclear Stability (Diagram)

Graph showing the relationship between neutron and proton numbers in stable nuclei against unstable nuclei

Nuclear Structure

The nucleus of an atom consists of nucleons (protons and neutrons)
Atomic number (Z) represents the number of protons
Nucleon number (A) represents the total number of protons and neutrons
Notation for an atom is often expressed by the chemical symbol and nucleon number (A)
Atoms of the same element can have different numbers of neutrons. These are called isotopes.

Nuclear Structure (Radius)

Nuclei are clustered together to form a spherical region
The radius of the nucleus depends on the atomic mass A by a formula (r ≈ (1.2×10⁻¹⁵ m) A^(1/3))
Isotopes: Nuclei with the same number of protons (Z) but different mass numbers (A)

Ionizing vs. Nonionizing Radiation

EM radiation with higher frequency than near-UV removes electrons, producing ionized atoms/molecules
This is called ionizing radiation
Lower-frequency radiation is non-ionizing (e.g., visible light)

Additional Slides (Self Study)

Radioactivity

Unstable nuclei undergo radioactive decay to achieve stability by emitting different particles or transforming nucleons.
Unstable nuclei change their number of protons and neutrons
The process is accompanied by the emission of energy.
The emission can be particulate or electromagnetic.

Alpha Decay

An alpha particle is a helium nucleus (²⁴He)
It has a charge of +2e and a nucleon number of 4
Alpha decay involves the emission of an alpha particle and the release of energy (kinetic energy) shared between the alpha particle and recoiling daughter nucleus

Alpha Decay (calculations)

Mass conservation is imperative in alpha decay; the total initial mass before decay equals the total mass after decay. There is slight mass difference that represents released binding energy

Beta Decay

A beta particle is an electron (⁻₁e) with a negative charge (-e)
Beta decay transforms a neutron into a proton (or vice-versa) which means there is a change in the number of protons in the nucleus
Beta decay is accompanied by the emission of an antineutrino

Neutrino and Antineutrino

Neutrinos are neutral subatomic particles with small mass and half-integral spin
Rarely interact with normal matter
Created in radioactive or nuclear reactions, as well as when cosmic rays hit atoms.
Antineutrinos are the antiparticles of neutrinos
Emitted during beta decay.

Beta+ Decay

Beta particle is a positron (+₁e) with a positive charge (+e)
Beta plus decay converts a proton in a nucleus to a neutron
Accompanied by emission of a neutrino

Beta+ Decay (Medical Applications)

Positron emitters are used in PET scans for functional imaging
A positron emitter radionuclide is injected into an area and accumulates in a tissue
Positrons undergo annihilation with electrons, resulting in two gamma photons emitted at opposite directions which are detected for diagnostic purposes.

Electron Capture

An orbital electron (from inner shells, K or L) is captured by a proton in the nucleus
This process forms a neutron
Accompanied by emission of a neutrino

Gamma Decay

EM radiation emitted as the nucleus goes from one excited state to a lower energy state/ground state
Also produced if the nucleus is in a metastable excited state (isomeric state), the decay is called an Isomeric Transition
Gamma decay involves no change in the number of protons or neutrons in the nucleus

Internal Conversion Electrons

Alternative to gamma emission, internal conversion electrons are emitted when orbital electrons absorb the energy from the nucleus transitioning to a lower energy state, causing the ejection of an electron from the atom

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Description

This quiz covers the fundamental concepts of electromagnetic radiation, including its properties, types, and wave characteristics. Understand how EM waves travel, their measurable attributes, and the relationship between wavelength and frequency.