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The unit Hertz (Hz) is fundamentally defined as one cycle or event occurring per second.
Answer: True
The definition of one Hertz (Hz) signifies precisely one complete cycle or event occurring within a one-second interval.
The Hertz (Hz) is an SI derived unit, formally expressed in terms of SI base units as the reciprocal of the second (s⁻¹).
Answer: True
As an SI derived unit, the Hertz is dimensionally equivalent to the inverse of time (T⁻¹), specifically one cycle per second (s⁻¹), underscoring its role in measuring temporal frequency.
The precise definition of the SI second is intrinsically linked to the hyperfine transition frequency of the caesium-133 atom, which is standardized at exactly 9,192,631,770 Hertz.
Answer: True
The modern definition of the second relies on the highly stable atomic transition frequency of caesium-133, which is precisely 9,192,631,770 Hz. This establishes a fundamental metrological link between time and frequency.
The definition of the second based on the caesium-133 atom ensures the accuracy of the hertz unit because the atomic frequency is highly stable.
Answer: True
The definition of the second relies on the extremely stable and consistent frequency of the caesium-133 atomic transition. This precise atomic standard ensures the accuracy and reliability of the Hertz unit, which is defined in terms of cycles per second.
The Hertz (Hz) is the standard SI unit used to measure the duration of time.
Answer: False
The Hertz (Hz) is the SI unit for frequency, measuring the number of cycles or events per second. The standard SI unit for the duration of time is the second (s).
The dimension of the unit Hertz is represented as T¹, indicating it is directly proportional to time.
Answer: False
The dimension of the unit Hertz is T⁻¹ (reciprocal time), indicating an inverse relationship with time, not direct proportionality. It represents cycles per unit time.
What is the fundamental definition of the Hertz (Hz) unit, and what physical quantity does it quantify?
Answer: The number of cycles or events occurring per second.
The Hertz (symbol: Hz) is the standard SI unit for frequency. It quantifies the number of cycles or repeating events that occur within one second.
The Hertz is an SI derived unit. What is its dimensional equivalence in terms of SI base units?
Answer: 1/Time (T⁻¹)
The Hertz (Hz) is an SI derived unit. Its dimensional expression in terms of SI base units is the reciprocal of time, denoted as s⁻¹ or T⁻¹.
How is the SI base unit for time, the second, defined in relation to the Hertz?
Answer: The frequency of the caesium-133 hyperfine transition is defined as exactly 9,192,631,770 Hz.
The SI definition of the second is intrinsically tied to the frequency of the caesium-133 atom's hyperfine transition, which is standardized at exactly 9,192,631,770 Hertz. This atomic standard provides the basis for both units.
The unit hertz (Hz) is specifically used for measuring the rate of which type of events?
Answer: Periodic or cyclical events
The Hertz (Hz) unit is designated for quantifying the frequency of periodic or cyclical phenomena, representing the number of repetitions per second.
What is the relationship between frequency (f) and period (T) for a periodic event?
Answer: f = 1/T
For any periodic event, the frequency (f) is the reciprocal of its period (T), meaning f = 1/T. The period is the time duration of one cycle.
Which of the following is NOT a typical application where frequency is measured in Hertz or its multiples?
Answer: Mass of a chemical compound
Frequency, measured in Hertz, applies to periodic events like clock speeds, sound waves, and radio waves. Mass is a fundamental property measured in units like kilograms, not frequency.
Heinrich Rudolf Hertz's seminal experimental verification of electromagnetic waves was a pivotal contribution that led to the SI unit of frequency being designated in his honor.
Answer: True
Heinrich Rudolf Hertz's groundbreaking work in the late 19th century provided the first empirical evidence for the existence of electromagnetic waves, a discovery that profoundly influenced physics and technology, leading to the naming of the frequency unit, the Hertz, in his honor.
The unit of frequency, Hertz, is named after the Italian physicist Enrico Fermi.
Answer: False
The unit of frequency, Hertz (Hz), is named in honor of the German physicist Heinrich Rudolf Hertz, not Enrico Fermi.
Heinrich Rudolf Hertz, after whom the Hertz unit is named, lived primarily in the 20th century.
Answer: False
Heinrich Rudolf Hertz lived from 1857 to 1894, meaning his primary contributions and life occurred in the 19th century, not the 20th.
The name 'hertz' for the frequency unit was established by the International Electrotechnical Commission (IEC) in 1960.
Answer: False
The International Electrotechnical Commission (IEC) established the name 'hertz' in 1935. The General Conference on Weights and Measures (CGPM) officially adopted it into the SI in 1960.
The General Conference on Weights and Measures (CGPM) officially adopted the hertz unit in 1935.
Answer: False
The General Conference on Weights and Measures (CGPM) officially adopted the Hertz unit into the SI in 1960. The IEC established the name in 1935.
Identify the German physicist after whom the SI unit of frequency, the Hertz, is named.
Answer: Heinrich Rudolf Hertz
The unit of frequency, Hertz (Hz), is named in honor of Heinrich Rudolf Hertz, a distinguished German physicist.
What significant scientific contribution is Heinrich Rudolf Hertz known for?
Answer: Providing conclusive proof of the existence of electromagnetic waves
Heinrich Rudolf Hertz's experimental work conclusively demonstrated the existence of electromagnetic waves, validating Maxwell's theory and paving the way for radio technology.
The IEC established the name 'hertz' for the frequency unit in which year?
Answer: 1935
The International Electrotechnical Commission (IEC) formally established the unit name 'Hertz' in 1935.
Physical vibrations, such as those at the molecular and atomic levels, can occur across a vast spectrum of frequencies, ranging from femtohertz (10⁻¹⁵ Hz) to terahertz (10¹² Hz) and beyond.
Answer: True
The study of molecular and atomic dynamics involves frequencies spanning many orders of magnitude, from the femtohertz range for very slow oscillations to the terahertz range for rapid vibrations.
Visible light falls within the frequency range of approximately 400 terahertz (THz) to 790 THz.
Answer: True
The electromagnetic spectrum corresponding to visible light spans frequencies from approximately 400 THz (red end) to 790 THz (violet end).
X-rays and gamma rays are electromagnetic radiations characterized by extremely high frequencies, often measured in the exahertz (EHz) range, corresponding to 10¹⁸ Hz.
Answer: True
X-rays and gamma rays represent the highest frequency portions of the electromagnetic spectrum, with frequencies commonly expressed in the exahertz (10¹⁸ Hz) range.
Pulsar timing arrays are employed to detect gravitational waves in the nanohertz (nHz) frequency range.
Answer: True
Pulsar timing arrays utilize the precise timing of radio pulses from pulsars to detect the subtle distortions caused by gravitational waves in the nanohertz frequency band.
The energy of a photon of electromagnetic radiation is directly proportional to its frequency, as described by the Planck relation E = hν.
Answer: True
The Planck relation (E = hν) fundamentally states that the energy (E) of a photon is directly proportional to its frequency (ν), with the Planck constant (h) as the constant of proportionality.
Terahertz radiation is electromagnetic radiation found between the radio frequency spectrum and the X-ray portion of the spectrum.
Answer: False
Terahertz (THz) radiation occupies the frequency range intermediate between radio waves (specifically microwaves) and infrared light, not X-rays.
Wavelength is always preferred over frequency (in Hertz) for describing light and higher frequency electromagnetic radiation due to SI standardization.
Answer: False
While wavelength and photon energy are often used for convenience, SI standards do not mandate wavelength over frequency for all electromagnetic radiation. Both are valid descriptors, and frequency is fundamental.
Gravitational waves detected by LIGO are observed in the nanohertz (nHz) frequency range.
Answer: False
Gravitational waves detected by LIGO are typically in the Hertz (Hz) range (30-7000 Hz). Nanohertz (nHz) frequencies are targeted by pulsar timing arrays.
Which of the following electromagnetic radiations has frequencies typically measured in the Terahertz (THz) range?
Answer: Visible light
Visible light falls within the frequency range of approximately 400 terahertz (THz) to 790 THz. Radio waves and microwaves are typically lower frequency, while X-rays are higher frequency.
Terahertz radiation occupies a frequency range in the electromagnetic spectrum that is intermediate between which two types of radiation?
Answer: Radio waves and infrared light
Terahertz (THz) radiation occupies the frequency range intermediate between the highest radio frequencies (microwaves) and infrared light.
Frequencies measured in exahertz (EHz) are characteristic of which type of electromagnetic radiation?
Answer: Gamma rays
X-rays and gamma rays are electromagnetic radiations characterized by extremely high frequencies, often measured in the exahertz (10¹⁸ Hz) range.
Why might wavelength or photon energy be preferred over frequency (in Hertz) for describing light?
Answer: Wavelength and photon energy are simpler to measure and conceptualize for light.
For historical reasons and practical measurement convenience in certain scientific contexts, such as spectroscopy, wavelength and photon energy are often employed instead of frequency (in Hertz) to describe light and higher-frequency electromagnetic radiation.
Gravitational waves detected by instruments like LIGO typically fall within which frequency range?
Answer: 30 Hz to 7000 Hz
Gravitational waves detected by instruments like LIGO are observed within the frequency range of approximately 30 Hz to 7000 Hz.
Which method is used to detect gravitational waves in the much lower nanohertz (nHz) frequency range?
Answer: Pulsar Timing Arrays
Pulsar timing arrays utilize the precise timing of radio pulses from pulsars to detect gravitational waves in the nanohertz (nHz) frequency band.
The pitch of a sound is perceived by humans based on the frequency of its sound wave, measured in Hertz.
Answer: True
The subjective perception of pitch in sound is directly correlated with the objective measurement of the sound wave's frequency in Hertz; higher frequencies correspond to higher perceived pitches.
An infant's ear can typically perceive frequencies up to 16,000 Hz, while adults can perceive up to 20,000 Hz.
Answer: False
Infants can typically perceive frequencies up to 20,000 Hz, while the upper limit for adults generally decreases with age, often below 20,000 Hz, and commonly cited as around 16,000 Hz.
Ultrasound waves have frequencies below the lower limit of human hearing, while infrasound waves have frequencies above the upper limit.
Answer: False
Ultrasound waves possess frequencies above the upper limit of human hearing (typically > 20,000 Hz), whereas infrasound waves have frequencies below the lower limit (typically < 20 Hz).
How does the frequency of sound waves relate to the pitch perceived by humans?
Answer: Higher frequency corresponds to higher pitch.
The subjective perception of pitch in sound is directly correlated with the objective measurement of the sound wave's frequency in Hertz; higher frequencies correspond to higher perceived pitches.
What frequency range defines ultrasound, which is typically beyond human hearing?
Answer: Above 20,000 Hz
Ultrasound refers to sound waves with frequencies exceeding the upper limit of human hearing, typically defined as frequencies above 20,000 Hertz (Hz).
What is the typical frequency range for the average adult human's hearing?
Answer: 20 Hz to 16,000 Hz
The typical range of frequencies audible to the average adult human extends from approximately 20 Hertz (Hz) to 16,000 Hertz (Hz), though this can vary with age and individual factors.
The concept known as the 'Megahertz myth' posits that clock speed, typically measured in Megahertz (MHz) or Gigahertz (GHz), is erroneously considered the sole determinant of Central Processing Unit (CPU) performance.
Answer: True
The 'Megahertz myth' highlights the fallacy of relying solely on clock speed for CPU performance evaluation. Factors such as architectural efficiency, instruction set complexity, and pipeline design significantly influence actual computational throughput, often rendering direct MHz comparisons misleading.
Early personal computer CPUs in the late 1970s operated at clock speeds typically exceeding 1 GHz.
Answer: False
Early personal computer CPUs in the late 1970s operated at clock speeds around 1 MHz, significantly lower than 1 GHz.
Modern CPUs like IBM's Power microprocessors can reach clock speeds up to 6 MHz.
Answer: False
Modern high-performance CPUs, such as IBM's Power microprocessors, can reach clock speeds up to 6 GHz, not 6 MHz.
The "Megahertz myth" critiques the use of clock speed (MHz/GHz) as the primary measure of CPU performance because:
Answer: Performance depends on factors beyond clock speed, like architecture.
The 'Megahertz myth' highlights that CPU performance is influenced by numerous factors beyond clock speed, including architectural design, instruction set efficiency, and cache performance, making clock speed alone an insufficient metric.
What was the approximate clock speed of early personal computer CPUs in the late 1970s?
Answer: 1 MHz
Early personal computer CPUs in the late 1970s operated at clock speeds around 1 MHz, significantly lower than modern processors.
What does the 'Megahertz myth' imply about comparing CPUs based solely on their clock speed rating?
Answer: Comparisons based solely on MHz can be misleading.
The 'Megahertz myth' suggests that relying solely on clock speed (MHz/GHz) for CPU comparisons can be misleading, as other architectural factors significantly impact overall performance.
Kilohertz (kHz) and megahertz (MHz) are common SI multiples of the Hertz unit used for expressing high frequencies.
Answer: True
Kilohertz (10³ Hz) and megahertz (10⁶ Hz) are standard SI prefixes used to denote multiples of the Hertz, facilitating the expression of higher frequency values.
The relationship between frequency (f) measured in Hertz and angular velocity (ω) measured in radians per second is defined by f = ω / (2π).
Answer: True
Angular velocity (ω) represents the rate of change of angular displacement and is related to frequency (f) by the formula ω = 2πf, or conversely, f = ω / (2π).
The unit Hertz (Hz) is specifically used for measuring the rate of periodic or cyclical events, while units like Becquerel (Bq) are used for random events like radioactive decay, despite both having the dimension of T⁻¹.
Answer: True
While both Hertz and Becquerel represent one event per second, Hertz is exclusively used for periodic or cyclical phenomena, whereas Becquerel is specifically designated for stochastic (random) events, such as radioactive decay.
In English, the plural form of 'hertz' is 'hertzes'.
Answer: False
In English, the plural form of the unit 'hertz' is also 'hertz.' This is a common convention for units named after individuals.
What is the correct plural form of the unit 'hertz' in English?
Answer: Hertz
In English, the plural form of the unit 'hertz' is also 'hertz.' This is a common convention for units named after individuals.
Which of the following is a common SI multiple of the hertz used for very high frequencies?
Answer: Gigahertz (GHz)
Gigahertz (GHz), representing 10⁹ Hz, is a common SI multiple used for expressing very high frequencies, particularly in computing and telecommunications.
What unit did the hertz replace when it was officially adopted into the SI by the CGPM in 1960?
Answer: Cycles per second (cps)
Upon its adoption into the SI by the CGPM in 1960, the Hertz replaced the term 'cycles per second' (cps) and its multiples (e.g., kc/s, Mc/s) as the standard unit for frequency.
Which of the following phenomena, despite having the dimension of T⁻¹, is NOT typically measured using the unit hertz?
Answer: Angular velocity
Although angular velocity shares the dimension of T⁻¹, it is measured in radians per second (rad/s), not Hertz. Hertz is specifically reserved for cyclical events.
How are frequencies in the range of 10¹² Hz commonly expressed?
Answer: Terahertz (THz)
Frequencies in the range of 10¹² Hz are commonly expressed using the Terahertz (THz) unit, where 1 THz = 10¹² Hz.
How should the unit name 'hertz' be capitalized when written out in full, following standard English rules?
Answer: Never capitalized (hertz)
When written out in full, 'hertz' follows the rules of a common noun and is only capitalized at the beginning of a sentence or in titles. The symbol 'Hz' is capitalized because the unit is named after an individual.