X Rays And The Ordering Of The Elements

When high-energy electrons collide with a metal target, they decelerate rapidly, causing them to lose energy in the form of electromagnetic radiation. The energy lost is emitted as X-rays, a type of electromagnetic radiation with wavelengths shorter than ultraviolet radiation. This process is the principle behind the generation of X-rays in X-ray tubes. Thus, the correct answer is .

Let’s break this down step by step to calculate the minimum wavelength of X-rays produced by 20 keV electrons and determine why option (1) is the correct answer.
Step 1: Understand the concept of minimum wavelength of X-rays
The minimum wavelength ( ) of X-rays produced by electrons occurs when all the kinetic energy of the electron is converted into the energy of the X-ray photon. This is given by:

A practical formula in electron volts and angstroms is:

where .
Step 2: Identify the given values and calculate the wavelength

• Energy of electrons,

This is approximately 0.62 \AA.
Step 3: Confirm the correct answer
The calculated minimum wavelength is 0.62 \AA, which matches option (1). The term “nearly” in the question accounts for slight rounding.
Thus, the correct answer is (1) 0.62 \AA.