Question

For the photoelectric effect, the maximum kinetic energy $E_k$ of the photoelectrons is plotted against the frequency $\nu$ of the incident photons as shown in figure. The slope of the graph gives

• A. Planck’s constant
• B. Charge of electron
• C. Work function of the metal
• D. Ratio of Planck’s constant to electric charge

Answer 1

Answer: (A)

Planck’s constant

Answer 2

The photoelectric effect is described by the equation:

$E_k = hf - \phi$

where:
- $E_k$ is the kinetic energy of the emitted electrons,
- $h$ is Planck’s constant,
- $f$ is the frequency of the incident photons,
- $\phi$ is the work function of the metal.

When the equation is rearranged in the form of $y = mx + b$:

$E_k = hf - \phi,$

where:
- $E_k$ corresponds to $y$,
- $f$ corresponds to $x$,
- $h$ (Planck’s constant) is the slope $m$,
- $-\phi$ is the y-intercept.

Thus, the slope of the graph, which represents the relationship between kinetic energy and frequency, gives Planck’s constant $h$.