8 · Radiation: benefits and harms

Light is only one kind

The light we see is only one type of electromagnetic (EM) radiation. While we can see the rainbow colours of visible light, there are other types of EM radiation that we cannot see — including infrared radiation and ultraviolet (UV) radiation.

Sunlight contains more than white light: it carries UV radiation too, which is invisible.

Some animals can see what we cannot Snakes can see infrared radiation — which is why a warm animal glows to them in the dark. Bees can see ultraviolet, so many patterns on flowers that are invisible to us are obvious to a bee, helping it find nectar easily.

The three radiations

Read the two lists side by side. In every case the useful property and the harmful one are the same property — it is the dose and the context that differ.

The pattern to notice

Radiation	Useful because…	Harmful because…
Infrared	…warm objects emit it, so a camera can map body temperature and screen for fever.	…it carries heat energy. Overexposure in welding and furnaces damages the eyes, and infrared trapped in the atmosphere drives climate change.
Ultraviolet	…it triggers chemical changes in living tissue — making vitamin D, treating psoriasis, and killing microorganisms in sterilisation.	…the same chemical changes damage the cells of our eyes and skin, causing skin cancer.
Visible light	…it lets plants photosynthesise and lets us see, work and travel safely after dark.	…it causes chemical changes that fade documents and paintings, and too much artificial light becomes light pollution.

Light pollution

Light pollution is where there is too much artificial light in the environment. It harms living things that depend on Earth's cycle of day and night to carry out life-sustaining activities such as migration, reproduction, searching for food, sleeping and escaping from predators.

Migratory birds gauge the change of seasons from the amount of sunlight, and so decide when to migrate. Artificial lights disrupt this, making them migrate too early or too late — which can be fatal, as they may miss the ideal climate for nesting and an adequate food supply.
Turtle hatchlings hatch at night and are guided to the sea by natural light in the sky. Artificial lamps draw them away from the sea, resulting in their deaths. In 2018 NParks launched Singapore's first turtle hatchery at the Sisters' Islands Marine Park.
Lighting the streets also uses a lot of electricity. Energy-efficient lighting such as LEDs and compact fluorescents (CFLs) reduces both light pollution and energy use.

From Edison to LEDs Thomas Edison developed the first commercial incandescent light bulb in 1879. Earlier inventors had made bulbs, but Edison's became popular because it was relatively inexpensive and long-lasting. He failed many times first, and regarded those failures not as failures but as discovering ways in which things did not work. Since then we have moved to energy-saving fluorescent lamps and LEDs.

Light is only one kind

The three radiations

The pattern to notice

Light pollution

Check yourself