Question

To understand the experiment that led to the discovery of the photoelectric effect.

In 1887, Heinrich Hertz investigated the phenomenon of light striking a metal surface, causing the ejection of electrons from the metal. The classical theory of electromagnetism predicted that the energy of the electrons ejected should have been proportional to the intensity of the light. However, Hertz observed that the energy of the electrons was independent of the intensity of the light. Furthermore, for low enough frequencies, no electrons were ejected, no matter how great the intensity of the light became. The following problem outlines the methods used to investigate this new finding in physics: the photoelectric effect.

 

A)Classical electromagnetism predicted that

V0  should have increased as the intensity of the incident light increased. On the contrary, it was found that V0  increased as the frequency f  of the light increased. The voltage V0  was found to obey the following linear relationship:

V0=mf-b  ,

where m  and b  are numerical constants (representing the slope and the intercept, respectively). By comparing this equation to your answer from Part B, find an expression for the intercept b . (Notice that mf  in this equation changes with different light but b  is a constant of the metal.)

Express your answer in terms of ∅  and e .

 

B)In a 1905 paper that later won him a Nobel Prize, Albert Einstein postulated that the energy of light was proportional to its frequency. The constant of proportionality turned out to be Planck's constant

h : Elight=hf  . Using your previous results, and the equation given in Part C, find an expression for h  in terms of experimentally determinable quantities.

Express your answer in terms of the slope m  and e .

Answer 1