Derive the formula for the maximum kinetic energy of an electron emitted from a metal with work function energy p , that is illuminated by light of frequency f.

MYTUTOR SUBJECT ANSWERS

Answers / Physics / A Level / Derive the formula for the maximum kinetic energy of an electron emitted from a metal with work function energy p , that is illuminated by light of frequency f.

1277 views

Derive the formula for the maximum kinetic energy of an electron emitted from a metal with work function energy p , that is illuminated by light of frequency f.

The phenomenon this question relates to is the photoelectric effect, and it can only be explained using Einstein’s photon model of light.

Electromagnetic waves are emitted in discrete lumps of energy, called photons.

The energy carried by one of these photons is given by E = hf = hc/l where l is the wavelength of the wave ( f=c/l ) , and h is the planks constant.

If a photon collides with a free electron in the surface of the metal, then the electron absorbs all of the energy of the photon. So the electron gains energy equal to hf.

However, energy is required to remove this electron from the metal. This is due to the negative charge of the electron and the positive charge of the nuclei in the metal atoms causing an attraction between them.

The energy required to remove the electron is the 'work function energy', p.

So the maximum kinetic energy that an electron can have once it has absorbed a photon and left the metal is KE = hf – p.

This is because the electron initially gains ‘hf’ of kinetic energy from the photon but then loses ‘p’ energy as it does work against the forces holding it in the metal.

George R. A Level Further Mathematics tutor, A Level Maths tutor, A ...

2 years ago

Answered by George, an A Level Physics tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

104 SUBJECT SPECIALISTS

Giorgos A. A Level Maths tutor, GCSE Maths tutor, A Level Physics tut...

View profile

£20 /hr

Giorgos A.

Degree: Mechanical Engineering with Renewable Energy (Masters) - Edinburgh University

Subjects offered:Physics, Maths

“Feel rewarded helping younger students. Nobody is born knowing everything, life is a learning process and my aim is to help you achieve your goals.”

Trusted by schools

| 5 completed tutorials

Save profile

Henri F. GCSE Electronics tutor, A Level Electronics tutor, GCSE Math...

View profile

£36 /hr

Henri F.

Degree: Aerospace Engineering PhD Spacecraft Control (Doctorate) - Bristol University

Subjects offered:Physics, Maths+ 4 more

“Aerospace Engineering PhD candidate in spacecraft control with 7 years of experience in tutoring.”

5.0

25 reviews | 58 completed tutorials

Save profile

Zubair M. 13 Plus Maths tutor, IB Maths tutor, A Level Maths tutor, ...

View profile

£20 /hr

Zubair M.

Degree: Theoretical Physics (Masters) - Leeds University

Subjects offered:Physics, Maths+ 1 more

“Organised Motivated Targeted Studious Focused Adaptable Experienced Proficient Academic”

4.8

8 reviews | 9 completed tutorials

Save profile

See more A Level Physics tutors

About the author

View profile

George R.

Currently unavailable: for regular students

Degree: Mathematics (Bachelors) - Cambridge University

Subjects offered:Physics, Maths+ 2 more

“A friendly and patient mathematics undergraduate, I enjoy helping students improve their understanding and gain confidence.”

4.9

7 reviews | 32 completed tutorials

Save profile

Version:	3.48.0
Build:	c981a57a9cf4
Time:	2017-07-24T15:36:26Z

MYTUTOR SUBJECT ANSWERS

Derive the formula for the maximum kinetic energy of an electron emitted from a metal with work function energy p , that is illuminated by light of frequency f.

Still stuck? Get one-to-one help from a personally interviewed subject specialist

104 SUBJECT SPECIALISTS

About the author

You may also like...

Posts by George

Other A Level Physics questions

One-to-one help is at your fingertips