When a beam of light shines on a metal surface, there is the possibility that el
ID: 1448209 • Letter: W
Question
When a beam of light shines on a metal surface, there is the possibility that electrons may be released from the surface of the metal. These electrons are usually called photoelectrons. The maximum kinetic energy of the photoelectrons are given by the following equation: KEmax = h f - W where h is Plancks' constant, f is the frequency of the light, and W is the workfunction of the metal surface. A scientist is performing a series of measurement using different colors of light as well as different metal surfaces.
17. Which of the following beams of light will result in the largest maximum kinetic energy of the photoelectrons?
A) Yellow light B) Violet light C) Green light D) Blue light E) Red light
18. On a particular surface, the scientist finds that the green light does not result in any photoelectrons emitted from the surface. Which of the following is true for this surface?
A) Both red and yellow light will not cause any photoelectrons to be emitted.
B) Orange and red light will not result in photoelectrons, but yellow light may.
C) An increase in the intensity of the green light may result in the emission of photoelectrons. D) Red light will result in photoelectrons, but yellow light will not.
E) Yellow light will result in photoelectrons, but blue light will not.
20. A metal surface is illuminated with violet light and electrons are ejected at a given rate with a certain maximum kinetic energy. If the intensity of the light is increased, electrons are ejected ____
A) at higher rate, but with a reduced maximum kinetic energy
B) at higher rate and with no change in their maximum kinetic energy
C) at higher rate and with higher maximum kinetic energy
D) at the same rate, but with higher maximum kinetic energy
Explanation / Answer
17)As energy of the beam is indirectly proportional to wavelength of the light, light with least wavelength will result in maximum K.E so violet light (B) is the answer.
18) As green light does not eject any electrons, light having wavelength greater than green light does not eject electrons. So option A is the correct answer.
20) When the intensity is increased no of photons are incresed but not the energy associated with them, so rate of ejection of electrons increases, but the maxm K.E remains same. So the answer is option B.
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