Which of the following has smallest wavelength

Explanation:

Electromagnetic waves can be categorized based on their wavelengths and frequencies. The wavelength of a wave is inversely proportional to its frequency; thus, higher frequency waves have shorter wavelengths.

Here are the given options and their relative positions in the electromagnetic spectrum:

1) Yellow rays: These are visible light rays with wavelengths around 570-590 nm.

2) X-rays: These have much shorter wavelengths, ranging from about 0.01 nm to 10 nm.

3) β-rays: These are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei. They have wavelengths of the order of 10^-12 meters, similar to gamma rays.

4) γ-rays: These are electromagnetic waves with the shortest wavelengths in the spectrum, less than 0.01 nm.

Comparing the wavelengths:

Yellow rays > X-rays > β-rays > γ-rays

∴ The correct answer is option 4: γ-rays have the smallest wavelength.