Chapter 7.2, Problem 1RC

Interpretation Introduction

Interpretation:

The light with shortest and longest wavelength has to be identified from the kinetic energies of ejected electrons.

Concept Introduction:

Wavelength and frequency:

The distance between any two similar points of a wave is called wavelength.

Figure 1

Frequency is defined as number of wavelengths of a wave that can pass through a point in one second.  Hertz is a unit of frequency.  It is defined as cycles per second.  Increase in wavelength decreases frequency and vice-versa.  Therefore, wavelength and frequency are inversely proportional to each other.

Ejection of electrons:

Electrons present in metals are held by attractive force.  It requires higher frequency of light to eject electrons.  When the energy of photon matches the energy that binds metal electrons, then the light can free electrons from metals.  When higher frequency of light is used it not only eject electrons but also acquires some kinetic energy.