General Q&A for Class 12 · Page 173
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is the frequency of 20 to 20000?
The range 20 Hz to 20,000 Hz (20 kHz) represents the typical human hearing range. Young, healthy ears can detect sounds within this spectrum: 20 Hz to 250 Hz: Bass and low-frequency sounds 250 Hz to 4 kHz: Mid-range (most speech and music) 4 kHz to 20 kHz: High frequencies (treble, consonants, harmonics) Hearing sensitivity typically decreases with age, particularly at higher frequencies.
- GeneralClass 12All
What is 20,000 Hz called?
20,000 Hz (20 kHz) is called an ultrasonic frequency because it's at or beyond the upper limit of human hearing. Sounds above 20 kHz are classified as ultrasound. Many animals, including dogs, cats, bats, and dolphins, can hear frequencies well above this threshold. Ultrasonic frequencies have applications in medical imaging, cleaning, and industrial testing.
- GeneralClass 12All
What is a normal frequency range?
"Normal" varies by context: Human hearing: 20 Hz to 20,000 Hz Human voice: 85 Hz to 255 Hz (fundamental frequencies) Visible light: 430 THz to 770 THz AC electricity: 50 Hz or 60 Hz Radio FM: 88 MHz to 108 MHz Wi-Fi: 2.4 GHz or 5 GHz Each application has its optimal frequency range based on physical properties an
- GeneralClass 12All
What is 52 Hz frequency?
52 Hz is famously known as the frequency of the "world's loneliest whale," a whale that vocalizes at this unusual frequency instead of the typical 15-25 Hz range of other whale species. This frequency also falls within the low-frequency audio range, below the fundamental frequency of most musical instruments but audible to humans.
- GeneralClass 12All
What is 27 MHz frequency?
27 MHz falls within the high-frequency (HF) radio band. It's commonly used for: CB (Citizens Band) radio: Channel 1 starts at 26.965 MHz Remote control toys: Many RC cars and planes Industrial/scientific/medical devices Amateur radio: Nearby frequencies At 27 MHz, electromagnetic waves have a wavelength of approximately 11 meters.
- GeneralClass 12All
How is frequency measured?
Frequency is measured using several instruments: Frequency counters: Digital devices that count cycles per second Oscilloscopes: Display waveforms and calculate frequency Spectrum analyzers: Show frequency distribution of signals Tachometers: Measure rotational frequency (RPM) Software tools: Audio analysis programs for sound frequencies T
- GeneralClass 12All
Is 432 Hz a frequency?
Yes, 432 Hz is a legitimate frequency that some musicians prefer as an alternative tuning standard to 440 Hz. Proponents claim music tuned to A4 = 432 Hz sounds more harmonious or natural, though scientific evidence for special properties is limited. It's approximately 8 Hz lower than standard concert pitch, creating a slightly mellower sound.
- GeneralClass 12All
Why do we calculate frequency?
<p>We calculate frequency for numerous practical reasons:</p><ul><li><strong>Telecommunications</strong>: Tuning radios, TVs, and wireless devices</li><li><strong>Electrical engineering</strong>: Ensuring power systems operate correctly</li><li><strong>Medicine</strong>: Analyzing heart rhythms, brain waves, and diagnostic imaging</li><li><strong>Music</strong
- GeneralClass 12All
How to calculate 50 Hz frequency?
If you're working with 50 Hz (common electrical frequency in many countries), you can determine: Period: T = 1/50 = 0.02 seconds (20 milliseconds per cycle) Angular frequency: ω = 2πf = 2π(50) ≈ 314.16 rad/s Wavelength (for electromagnetic waves): λ = c/f = (3×10⁸)/50 = 6,000,000 meters These calculations help in electrical system design and analysis.
- GeneralClass 12All
What is 50 Hz in electricity?
50 Hz is the standard alternating current (AC) frequency used in electrical power systems in Europe, Asia, Africa, and Australia. This means the current alternates direction 50 times per second, completing 50 full cycles. The voltage waveform oscillates between positive and negative peaks 50 times each second, which is optimal for power transmission and most electrical appliances in these regions.
- GeneralClass 12All
What does a frequency of 440 Hz mean?
440 Hz is the international standard pitch for the musical note A above middle C (A4). This frequency means the sound wave vibrates 440 times per second. Musicians use 440 Hz as a reference point for tuning instruments—when an instrument plays A4 at exactly 440 Hz, it's considered "in tune" with standard concert pitch.
- GeneralClass 12All
What formula is E = hc/λ?
This is the photon energy formula from quantum physics. It calculates the energy (E) of a photon based on its wavelength (λ), where: E = energy in joules h = Planck's constant (6.626 × 10⁻³⁴ J·s) c = speed of light (3 × 10⁸ m/s) λ = wavelength in meters This relates electromagnetic wave properties to quantum energy levels.
- GeneralClass 12All
How to find Hz frequency?
To find frequency in Hz: From period: Divide 1 by the time period (f = 1/T) From wave properties: Divide wave speed by wavelength (f = v/λ) Using measurement tools: Use an oscilloscope, frequency counter, or spectrum analyzer From audio: Use a tuner or frequency analysis software Always ensure your time measurements are in seconds to get Hz directly.
- GeneralClass 12All
What is the formula for wavelength λ?
The wavelength formula is λ = v/f, where: λ (lambda) = wavelength in meters v = wave velocity in meters per second f = frequency in Hertz This can be rearranged from the wave equation v = fλ to solve for wavelength when you know velocity and frequency.
- GeneralClass 12All
What are the two formulas for frequency?
The two primary formulas for calculating frequency are: f = 1/T (using period) f = v/λ (using wave velocity and wavelength) Both formulas give you frequency in Hertz, but you'll use the first when you know the time per cycle and the second when dealing with wave properties.
- GeneralClass 12All
What is the basic formula for frequency?
The most fundamental frequency formula is f = 1/T, where: f = frequency (Hz) T = period or time for one cycle (seconds) This formula shows that frequency and period are inversely related—higher frequency means shorter period, and vice versa.
- GeneralClass 12All
How do we calculate frequency?
Frequency can be calculated using the basic formula: f = 1/T, where f is frequency in Hertz and T is the period (time for one complete cycle) in seconds. Alternatively, for waves, use f = v/λ, where v is wave velocity and λ (lambda) is wavelength. Choose the formula based on the information available.
- GeneralClass 12All
What are the three formulas for speed?
The three main formulas related to speed are: Speed = Distance ÷ Time Distance = Speed × Time Time = Distance ÷ Speed These are rearrangements of the same relationship between speed, distance, and time.
- GeneralClass 12All
How much distance will be covered by a car in 24 seconds at 45 km/h?
First convert 45 km/h to meters per second: 45 × 1000 ÷ 3600 = 12.5 m/s Distance = 12.5 m/s × 24 seconds = 300 meters (or 0.3 km)
- GeneralClass 12All
What is the average speed of driving 30 km?
You cannot determine average speed from distance alone. You need to know how long it took to drive 30 km to calculate the average speed.