Statement-1: In the process of photo electric emission, all the emitted photoelectrons have same K.E.

Statement-2: According to einstein's photo electric equation KE_max = hn – f.

a)
Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1.

b)
Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1.

c)
Statement-1 is true, statement-2 is false.

d)
Statement-1 is false, statement-2 is true.

Correct answer is option 'D'. Can you explain this answer?

Question

Statement-1: In the process of photo electric emission, all the emitted photoelectrons have same K.E.

Statement-2: According to einstein's photo electric equation KE_max = hn – f.

a)
Statement-1 is true, statement-2 is true and statement-2 is correct explanation for statement-1.
b)
Statement-1 is true, statement-2 is true and statement-2 is NOT the correct explanation for statement-1.
c)
Statement-1 is true, statement-2 is false.
d)
Statement-1 is false, statement-2 is true.

Correct answer is option 'D'. Can you explain this answer?

Answer

When light of frequency f is incident on a metal surface that has a work function W, the maximum kinetic energy of the emitted electrons is given by:
KEmax=hf−ϕ
Note that this is the maximum possible kinetic energy because ϕ is the minimum energy necessary to liberate an electron.Increasing the frequency of the incident beam, keeping the number of incident photons fixed increases the maximum kinetic energy of the photoelectrons emitted.So, Statement-1 is False, Statement-2 is False.

Answer

Correct Answer :- d

Explanation : a) Metals emit electrons when light shines upon them. The phenomenon is named as photoelectric effect and the electrons emitted in such manner are called photoelectrons.

The kinetic energy of photoelectrons vary simply because of the fact that (after photoelectric effect has taken place) all the photoelectrons are not emitted instantly. Most of the photoelectrons first collide (several times!) with the other electrons (which are roaming around with random velocities; recall that metals are generally electrically conductive i.e. having abundant free electrons) within the metal. These photoelectrons lose some fraction of their kinetic energy in such collisions before they are emitted out of the metal.

That's why it is observed that the photoelectrons do not have the same kinetic energy.

b) In the photoelectric effect, each photon donates all of its energy hf to an electron in the metal. If this process occurs at the metal surface, the electron is released into the vacuum with a kinetic energy given by:

Kmax = hf - phi

Answer

Explanation:

Statement 1: In the process of photoelectric emission, all the emitted photoelectrons have the same kinetic energy.
- This statement is false because in the photoelectric effect, the kinetic energy of the emitted photoelectrons can vary depending on the energy of the incident photons.

Statement 2: According to Einstein's photoelectric equation, $ K_{Emax} = h\nu - f $.
- This statement is true. The equation relates the maximum kinetic energy of the emitted photoelectrons ($ K_{Emax} $) to the frequency of the incident light ($ \nu $) and the work function of the material ($ f $).
Therefore, the correct answer is:

Statement-1 is false, statement-2 is true.

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