I am not sure but it may be chronologist.
Scientists who study rainbows are called atmospheric scientists or optical physicists. They study the physics behind the formation and properties of rainbows, including how light is refracted, reflected, and dispersed in the atmosphere to create this colorful phenomenon.
Somnology or hypnology
They are called astronomers.
People who study light are called "optical scientists" or "optical physicists." They research and study the properties, behaviors, and applications of light, which is a vital aspect of physics and engineering disciplines.
A weather scientist is called a meteorologist.
When scientists study plants, it is called Botany.
Scientists who study earth's oceans are called oceanographers.
Scientists who study Earth's surface and interior are called Geologists.
because they study about Science
Scientists who study caves are called speleologists
The scientists who study genetics are called geneticists.
Scientists who study rocks are called geologists. They specialize in the field of geology, which includes the study of the Earth's history, structure, and processes, including the formation and properties of rocks.
Generically they are called "biologists" There are also specializations such as Zoologist (study of animals) Botanist (study of plants) etc.
Scientists who study genetics are called geneticists. They specialize in the field of genetics, which involves the study of genes, heredity, and genetic variations.
pure
Mycologists.
Ichthyologists.