What technique can I use to visualize (directly observe) the fragments of DNA?

DNA fragments can be visualized using the gel electrophoresis technique.

To visualize DNA fragments, an agarose gel medium is stained with a DNA-binding dye before electrophoresis. The sample to be tested is then placed on the dyed gel. When an electric current is applied to the gel, the negatively charged DNA fragments migrate towards the positive electrode at varying speeds depending on their size. The smaller fragments move through the gel faster than the larger fragments, allowing them to be separated according to size. By the time the gel electrophoresis process is complete, each DNA molecule would have picked up a significant amount of the dye.

When placed under UV light, the DNA fragments glow, allowing you to see the fragments present at different locations along the length of the gel. The DNA fragments can be seen as bands, with each band containing a group of same-sized DNA fragments.