Researchers shine a blue light with a frequency of about 500 nm on a metal surface. No photoelectric effect is observed. To increase the chance of observing the effect, what color light should the researchers try? A.
violet
B.
green
C.
orange
D.
red

Australopithecus robustus was likely the longest-surviving species of australopithecine in south africa. it had: a. large molars, a big face, and a sagittal crest. b. a large body, large teeth, and a sagittal crest. c. a big brain, big teeth, and a big face. d. a big face, large teeth, and a large body