Question

Can you help me with this hw question?Due to the Doppler effect, waves from an approaching source (moving toward the observer) are observed as having a shorter wavelength than when they were emitted. Which of the following pairs could represent the kind of radiation emitted from a source rapidly approaching Earth and the kind of radiation it is detected as on Earth?Aemitted as a gamma ray, observed as ultraviolet lightBemitted as a microwave, observed as a radio waveCemitted as yellow light, observed as blue lightDemitted as ultraviolet light, observed as infrared radiation

Answer 1

Given that due to the Doppler effect, the emitted wavelength having a longer wavelength is observed to be a shorter wavelength.

So, we have to check each option for the emitted wavelength having a greater value and the observed wavelength having a smaller value.

(A)Gamma has a shorter wavelength which is emitted and ultraviolet light which is observed has a longer wavelength.

Thus, this option is wrong.

(B) Emitted microwave has a shorter wavelength than an observed radio wave.

Thus, this option is also wrong.

(C) Emitted yellow light has a longer wavelength than observed blue light.

Thus, this option is correct.

(D) Emitted ultraviolet has a shorter wavelength than the observed wavelength.

Thus, the option is incorrect.

Hence, option (C) is correct.