- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Although the Doppler shift is well understood, its demonstration using light is not simple. Using light is not simple because the moving mirror from which light is reflected cannot usually be moved in a sufficiently smooth and uniform manner to keep the level of noise below that of the signal. Small perturbations as small as the optical wavelength can produce a non-negligible noise. Instead, Doppler shift experiments for undergraduates are usually performed with sound or microwaves. Previous undergraduate demonstrations of the optical Doppler shift have involved the use of Michelson interferometers with arms of approximately equal path lengths using an air-track glider1 or a servo-mounted mirror on an isolated optics table;2 light reflection from Scotchlite tape on a rotating turntable with a spectrum analyzer;3 and direct frequency modulation produced by a model train engine.4 Velocities up to 0.3 m/ s were used, and thus Doppler beat frequencies were below 1 MHz.