question_answer

Ramesh and his younger brother Raju went to a shopping mall whose doors were automatic with self close and open. Raju asked Ramesh that, "How these doors automatically open and close without even a single touch?".

Ramesh was a graduate, but he did not know the exact reason behind this. Ramesh asked the same from his friend Rakesh who was junior to him. Rakesh explained the whole phenomenon easily to Ramesh and told that this whole phenomenon is based on photoelectric effect given by the great scientist Einstein.

(i) After reading the passage, what are your opinions about the education of Ramesh and describe about all three characters Ramesh, Rakesh and Raju in your words.

(ii) State the laws of photoelectric effect.

(iii) Write photoelectric equation given by Einstein and define photoelectric current.

Answer:

(i) Ramesh has not done its education properly. He is not a good student. Rakesh is good in studies. Raju is keen to know about the happenings around him.

(ii) The photoelectric emission is an instantaneous process. The time lag between the incidence of radiations and emission of photoelectrons is very small, less than even \[{{10}^{-\,9}}s.\]

(iii) Photoelectric equation is

\[{{K}_{max}}=hv-{{\phi }_{0}}\] Photoelectric current When radiation of suitable frequency fall on the surface of metal, then the emitted electrons are called photoelectron and current due to this emission of electron is called photoelectric current.