Physics
The bats can fly in the dark because

They have weak legs and are likely to be attacked by predators
They generate ultrasonic sound waves
They generate flashes of light
They can see the objects in darkness

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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 wavelength of X-ray photon is less than the wavelength of visible radiation photon.
The frequency of X-ray photon is higher than the frequency of visible radiation photon.

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