Which among the various techniques of stellar distance measurement is the best one? Discuss the merits and demerits of all the techniques (stellar parallax, using absolute and apparent magnitudes, using periods of variable stars, and red shifts of very distant objects).

Ultraviolet radiation is dangerous because it has a high enough energy to damage skin cells. what is the best explanation of the relationship between wavelength and wave energy? a) wave energy is related only to frequency, not wavelength. b) longer wavelengths have lower frequencies but higher energy. c) the shorter the wavelength, the lower the frequency and the higher the energy. d) the shorter the wavelength, the higher the frequency and the higher the energy.