Cuesta College, San Luis Obispo, CA
Google ATAP
youtu.be/0QNiZfSsPc0
Google's Project Soli[*] is developing a sensor that detects hand gestures using radio waves, with frequencies between 57 GHz to 64 GHz in air. In air, the 57 GHz radio wave has __________ wavelength compared to the 64 GHz radio wave.
(A) a shorter.
(B) a longer.
(C) the same.
(D) (Not enough information is given.)
[*] rarstechnica.com/gadgets/2019/01/googles-project-soli-radar-gesture-chip-isnt-dead-gets-fcc-approval/.
Correct answer (highlight to unhide): (B)
Wave speed v depends on the properties of the medium. Frequency f depends on the properties of the source. These two parameters can be varied independently of each other.
The wavelength λ is the parameter dependent on both of the independent parameters:
λ = v/f.
Since the two radio waves have the same speed v (as they travel through the same medium), then because of their different frequencies, they will have have different λ wavelengths (as this parameter depends on both the wave source and the properties of the medium):
λ1 = v1/f1,
λ2 = v2/f2,
where v1 = v2 (as both waves travel through air). With f1 = 57 GHz being lower than f2 = 64 GHz, then λ1 > λ2, and so the 57 GHz radio wave has the longer wavelength.
Sections 30882, 30883
Exam code: quiz01aN7u
(A) : 6 students
(B) : 28 students
(C) : 2 students
(D) : 1 student
Success level: 76%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.63
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