The Electromagnetic Spectrum

Humans and other animals can detect a range of wavelengths.

What is the Electromagnetic Spectrum?

The electromagnetic spectrum is a range of energy forms which all travel at the speed of light.

These forms vary in wavelength and frequency.

Which ones can humans detect?

Humans detect visible light which ranges from roughly 400nm to 700nm. This means that humans can only see objects within this wavelength.

All colours we can see fall into this category.

An easy way to remember the visible spectrum in its order of increasing energy is is through the acronym - ROY. G. BIV

What animals detect other wavelengths?

Snakes can detect infrared light (heat). They do this to detect prey and avoid predators. Infrared light falls between 750nm to 1mm in wavelength.

Bees use ultraviolet light to detect petals on plants. This leads the bees to a food source (nectar) and provides the plants with pollinators. U.V light ranges from 10nm to 400nm.

Why is it important to be able to detect a variety of different wavelengths?

Many organisms live in different niches. These niches produce different obstacles for the organism. Each organism needs to detect predator and prey within their environment to survive. This may come in the form of a different electromagnetic field. For example:

  • electric eels emit an electric field within their environment. Any disturbance to this environment such as that by prey is detected by the eel. Subsequently the prey is consumed. Eels use this form of electromagnetic radiation as vision within a water environment is quite poor.

  • The platypus has electromagnetic receptors in its bill. This helps the platypus to detect prey which produces an electric field. Platypuses use these receptors as vision within a water environment is quite poor.

  • Snakes use infrared light to detect predators and prey. This is due to the fact that snakes are largely found on the ground and in the underbrush of bushland. Snakes rarely use normal vision due to the lack of periphery on the ground.

  • Bees use ultraviolet light in detecting the nectar on flowering plants. This form of electromagnetic radiation is an advantage as the bee is able to quickly and efficiently detect a food source.

  • Humans use two single lens eyes to detect visible light. Humans have many photoreceptor cells of different pigment which detect the various colours of the spectrum. This form of electromagnetic radiation enables humans to produce sharp images of various objects.

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