Microscopes

Question 1

Why are stains used in microscopy?

Answer 1

Stains are used in microscopy as it increases contrast, makes cells more visible and makes it easier to identify different cell components.
E.g.

. iodine solution stains starch granules blue and black

. Methylene blue stains genetic material in animal cells blue

Question 2

What is magnification and resolution?

Answer 2

Magnification in the number of times greater the image size is then the actual object

Resolution is the ability to distinguish between two objects closely together clearly, high res has more details (better ability to distinguish between two objects)

Question 3

Write in detail everything about optical microscopes (res, mag, pros, cons and how it works)

Answer 3

Light microscopes useslight to form an image, this is done by light passing through or bouncing on the specimen. The magnification is up to x2000-1500x, and res is 200nm and can be used to observe living and non-living specimens. Lights wavelength is 400-700nm.

Advantages- easy to use, Relatively cheap, Portable, Used on whole living organisms

Disadvantages- Optical microscopes use visible light which have a wavelength of 400nm-700nm. This makes the resolution low so objects closer then 200nm are seen as one object, Ribosomes can’t be seen by optical isomers as ribosomes are very small and have a diameter of 20nm.

Question 4

Write in detail everything about Transmission electron microscopes

Answer 4

. uses a beam of electrons (0.004nm) to form an image, this happens by the detection of electrons being passed through the specimen. It provides a black and white 2d image of the inner structure, has a mag of x2000000, a resolution of 0.2nm and only non-living specimens can be observed. The reason the specimen is non-living is because the specimen must be dehydrated and stained.

Question 5

Write in detail everything about Scanning electron microscopes

Answer 5

uses beams of electrons (0.004nm) to form an image, it does this by the detection of electrons that are reflected from the surface of the specimen. This creates a black and white 3d image of the surface of a specimen (colour can be added). The mag is x200000, res Is 3-20nm and only dead or non-living specimens can be used. The specimens must be placed in a vacuum.

Question 6

advantages and disadvantages of electron microscopes

Answer 6

Both these electron microscopes have a high resolution (can observe ribosomes) whilst having a high magnification. They are both very large and expensive and require a lot of skill and training to use. The specimens also must be dead.

Question 7

Write in detail everything about laser scanning microscopes

Answer 7

LES uses laser beams to scan an object pixel by pixel to create a coloured 3d image from the reflection of the photons or can form a 2d image of high resolution and high contrast. Laser scanning microscopes can form depth selective images (images that you can focus on different depths). They can be used on whole living specimens. They are mostly used in the medical profession and in branches of biology.