Physics
The frequency of ultrasound wave is typically

Above 20 kHz
Below 02 kHz
Below 20 kHz
Above 20,000 kHz

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Physics
A photon of X-ray has energy of 1 keV. A photon of visible radiation has energy of 3 eV. In this context, which one of the following statements is not correct?

Both the photons have different energies.
The speeds of both the photons in vacuum are different
The frequency of X-ray photon is higher than the frequency of visible radiation photon.
The wavelength of X-ray photon is less than the wavelength of visible radiation photon.

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