Questions and Answers
What is Hertz used to measure?
Frequency
What is the frequency of the emitted gamma photons?
3.38 × 10^19 Hz
What minimal information is required for an ultrasound examination to image the motion of a fetus?
The speed of sound and the frequencies of the sound waves emitted and observed.
What does 10 dB equivalent to using 10 as the base?
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What is the equation of frequency in regards to wavelength?
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What does it mean for two waves to be in phase?
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What is the phase difference when two waves are in phase?
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If two waves are perfectly in phase, what is the amplitude of the resultant wave?
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What amplitude would the resultant wave have if two equal waves are exactly 180 degrees out of phase?
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What is destructive interference?
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What is period in terms of waves and how is it represented?
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Write the equation that relates the period (T) and frequency (f) of a wave.
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What speed do electromagnetic waves such as UV, radio waves, and microwaves travel at?
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Which option explains the discrepancy in the wavelength of hydrogen observed in a star's spectrum compared to its laboratory measurement?
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In regards to the visible light spectrum, different wavelengths of visible light correspond to different what?
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Study Notes
Units of Measurement
- Hertz (Hz) measures frequency, defined as the number of wavelengths passing a fixed point per second.
- Formula: Hz = 1/s (where s represents seconds).
Gamma Photons Frequency
- Frequency of emitted gamma photons (140-keV) is calculated as 3.38 × 10^19 Hz.
- Use the formula f = E/h with Planck's constant (h = 6.6 x 10^-34 Js).
Ultrasound Examination
- Ultrasound devices require sound speed and frequency of emitted and observed sound waves for fetal imaging.
Decibel Scale
- The decibel (dB) measures sound intensity.
- 10 dB equates to 10^1, and the pattern continues exponentially (20 dB = 10^2, etc.).
Frequency and Wavelength
- Frequency (F) is calculated using velocity and wavelength (ƛ): F = velocity / ƛ.
Wave Characteristics
- Waves are in phase when they have the same frequency, wavelength, and amplitude and pass through the same space simultaneously.
- Phase difference of in-phase waves is zero.
Resultant Wave Amplitude
- When two perfectly in-phase waves combine, the resultant wave's amplitude equals the sum of both waves' amplitudes.
- Two equal waves exactly 180 degrees out of phase result in zero amplitude.
Interference Types
- Destructive interference occurs when out-of-phase waves (crest of one coinciding with trough of another) counteract each other, resulting in zero amplitude.
Wave Period and Cycle
- Period (T) represents the time required to complete one full wavelength, expressed in seconds per cycle.
- Relationship between period and frequency is given by T = 1/f, where frequency is in seconds.
Speed of Waves
- Electromagnetic waves (UV, radio waves, microwaves) travel at the speed of light, which is faster than sound waves.
Doppler Effect and Astronomy
- Observed discrepancies in light wavelengths from stars indicate relative motion towards or away from Earth.
- A star emitting a shorter wavelength than laboratory measurements suggests it is approaching Earth, increasing observed frequency.
Spectrum of Visible Light
- Different wavelengths of visible light correspond to different colors, showing the spectrum's diversity.
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Description
This quiz covers essential concepts related to units of measurement in physics, including frequency, sound intensity, and wave characteristics. You'll explore calculations for gamma photons and ultrasound examination. Test your knowledge of formulas and the properties of waves and sound.
