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.

Similar Class 12 Doubts

Statement - 1 : A positive point charge initially at rest in a uniform electric field starts moving along electric lines of forces. (Neglect all other forces except electric forces)Statement - 2 : Electric lines of force represents path of charged particle which is released from rest in it.

Statement - 1 : For a non-uniformly charged thin circular ring with net charge zero, the electric potential at each point on axis of the ring is zero.Statement - 2 : For a non-uniformly charged thin circular ring with net charge zero, the electric field at any point on axis of the ring is zero.

Statement - 1 : If electric potential while moving in a certain path is constant, then the electric field must be zero.Statement - 2 : Component of electric field

Statement - 1 : The electric potential and the electric field intensity at the centre of a square having four fixed point charges at their vertices as shown in figure are zero.Statement - 2 : If electric potential at a point is zero then the magnitude of electric field at that point must be zero.

Top Courses for Class 12

Suggested Free Tests

Related Content

Schools

Competitive Examinations

Quick Access Links

Technical Exams