This site is not maintained. Click here for the new website of Richard Dawkins.

Cell Size and Scale

http://learn.genetics.utah.edu/content/begin/cells/scale/

Some cells are visible to the unaided eye

The smallest objects that the unaided human eye can see are about 0.1 mm long. That means that under the right conditions, you might be able to see an ameoba proteus, a human egg, and a paramecium without using magnification. A magnifying glass can help you to see them more clearly, but they will still look tiny.

Smaller cells are easily visible under a light microscope. It’s even possible to make out structures within the cell, such as the nucleus, mitochondria and chloroplasts. Light microscopes use a system of lenses to magnify an image. The power of a light microscope is limited by the wavelength of visible light, which is about 500 nm. The most powerful light microscopes can resolve bacteria but not viruses.

To see anything smaller than 500 nm, you will need an electron microscope. Electron microscopes shoot a high-voltage beam of electrons onto or through an object, which deflects and absorbs some of the electrons. Resolution is still limited by the wavelength of the electron beam, but this wavelength is much smaller than that of visible light. The most powerful electron microscopes can resolve molecules and even individual atoms.
...
Continue reading
http://learn.genetics.utah.edu/content/begin/cells/scale/


---

TAGGED: BIOLOGY, GENETICS


RELATED CONTENT

Bonobo makes stone tools like early...

Hannah Krakauer - New Scientist Comments

Kanzi the bonobo is able to create and use stone tools

Scientists Discover Previously Unknown...

- - URMC Comments

Newer Imaging Technique Brings ‘Glymphatic System’ to Light

Grey parrots use reasoning where...

- - The Royal Society Comments

Research suggesting that grey parrots can reason about cause and effect from audio cues alone- a skill that monkeys and dogs lack- is presented in Proceedings of the Royal Society B today.

Why do organisms build tissues they...

- - Science Blog Comments

Why, after millions of years of evolution, do organisms build structures that seemingly serve no purpose?

New flat-faced human species possibly...

Charles Choi - CBS News Comments

Four decades ago, in 1972, the Koobi Fora Research Project discovered the enigmatic fossilized skull known as KNM-ER 1470 which ignited a now long-standing debate about how many different species of early Homos existed.

A New Species Discovered ... On Flickr

Adam Cole - NPR Comments

One day in May of 2011, Shaun Winterton was looking at pictures of bugs on the Internet when something unusual caught his eye. It was a close shot of a green lacewing — an insect he knew well — but on its wing was an unfamiliar network of black lines and a few flecks of blue.

MORE

MORE BY LEARN.GENETICS UNIVERSITY OF UTAH

MORE

Comments

Comment RSS Feed

Please sign in or register to comment