Answer:
Quantum mechanics tells us that light can behave simultaneously as a particle or a wave. ... When UV light hits a metal surface, it causes an emission of electrons. Albert Einstein explained this "photoelectric" effect by proposing that light – thought to only be a wave – is also a stream of particles.
Explanation:
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The Answer is B because primary consumers need to get their food from plants.
I think so it ans wold be d.because if the source approaches the observer more and more wavefront will pass and it get squeezed.so wavelength decreases and frequency increases.