Size and scale: Key concepts in biology: Biology: GCSE (9:1)

Light microscope

Equipment which uses visible light to detect and magnify small objects

Electron microscope

A microscope that forms an image by focusing beams of electrons onto a specimen, has a higher resolution and magnification than light microscopes

Importance of electron microscopes

Allowed for an increased understanding of sub-cellular structures such as ribosomes, that are too small to view with a light microscope

Magnification

How much an image appears to have increased in size by

Resolution

The degree of detail visible in an image

Magnification equation

Magnification = size of image/size of real object

Standard form

A system where numbers are expressed as decimals between 1 and 10 and multiplied by a power of 10

Centi

A prefix meaning one hundredth of a unit

Milli

A prefix meaning one thousandth of a unit

Micro

A prefix meaning one millionth of a unit

Nano

A prefix meaning one thousand-millionth (now called a billionth) of a unit

Pico

A prefix equating to one million-millionth (now called a trillionth) of a unit

Image size

The size of an object on an image after magnification

Actual size

The actual or real size of an object before magnification

Sub-cellular structures

Structures or organelles that are found in the cell

Staining techniques

The use of dyes such as iodine or methylene blue to better see cells and sub-cellular structures under a light microscope

SI units

The preferred metric units for use in science such as metre, millimetre, micrometre

Micrometre

There are 1000 micrometres in a millimetre and 1000000 micrometres in a metre

Millimetre

There are 10 millimetres in a centimetre and 1000 millimetres in a metre

Picometre

There are 1000 picometres in a micrometre, 1000000 picometres in a millimetre and 10^12 picometres in a metre

Earliest microscopes

Dutch spectacle maker Janssen experimented with putting lenses in tubes in the 1590s, he made the first compound microscope that could have magnified from ×3 to ×9

Robert Hooke

British scientist, Robert Hooke (also famous for his law of elasticity in Physics) observed and drew cells using a compound microscope in the 1650s

Antonie van Leeuwenhoek

Dutch scientist who constructed a microscope with a single spherical lens in the late 1600s, it magnified up to ×275