Dr. murphy and dr. lee are scientists. they are looking at the same type of cells under a microscope. dr. murphy can see only the nucleus and the cell membrane. dr. lee can see the nucleus, the cell membrane, the endoplasmic reticulum, the ribosomes, and the mitochondria. what best describes this scenario?

Dr. Lee is using an electron microscope and Dr. Murphy is using a light microscope.

An electron microscope has higher magnification and higher resolution than light microscopes. That's why the person who is using it , Dr. Lee, can see smaller structures(endoplasmic reticulum, the ribosomes, and the mitochondria) with same type of cell under the microscope.
This is achived by using beams of electrons instead of rays of visible light, like light microscopes do,  to form highly magnified and high-resolution images of tiny areas of the cell.