Q)
Sona was often surprised by the reproduction of sound in cinemas. She asked her uncle about this. Even though her uncle didn’t know much about this, he decided to give Sona a clear picture about the reproduction of sound in cinemas. He went to the operator of the projector of the cinema hall and learnt about this. Then he took Sona to the projector room and the operator explained about this very clearly. She thanked her uncle.
A) What according to you are the values displayed by Sona’s uncle?
B) What is the role of Photoelectric effect in the reproduction of sound in cinema film?
C) State two different situation in which free electrons may be emitted from a surface.
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