A distant star is receding from the Earth with a speed of 1.4o x 107 m/s. It emits light of frequency 4.57 x 10^14 Hz. The speed of light is 3.0 x 10^8 m/s. The Doppler effect formula can be used with light waves. What will bethe frequency of this light when detected on Earth?
Correct answer: B. 4.36 x 10^14 Hz
- A. 2.04 x 10^13 Hz
- B. 4.36 x 10^14 Hz
- C. 4.57 x 10^14 Hz
- D. 4.79 x 10^14 Hz
Explanation
Given: v (receding speed) = 1.40 x 10^7 m/s f_source (emitted frequency) = 4.57 x 10^14 Hz c (speed of light) = 3.0 x 10^8 m/s Doppler effect formula for light: f_observed = f_source * sqrt((1 - v/c) / (1 + v/c)) Calculations: v/c = (1.40 x 10^7 m/s) / (3.0 x 10^8 m/s) = 0.0466666... sqrt((1 - v/c) / (1 + v/c)) = sqrt((1 - 0.0466666...) / (1 + 0.0466666...)) sqrt((1 - v/c) / (1 + v/c)) = sqrt(0.9533333 / 1.0466666) sqrt((1 - v/c) / (1 + v/c)) = sqrt(0.9108108) sqrt((1 - v/c) / (1 + v/c)) = 0.9543641 (approximately) f_observed = 4.57 x 10^14 Hz * 0.9543641 f_observed = 4.361936 x 10^14 Hz Result: f_observed = 4.36 x 10^14 Hz (approximately)
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Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.
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