LEARNING OBJECTIVES

  1. Understand that, over the years, microscopy techniques have improved.
  2. Know the difference in magnification and resolving power between light microscopes and electron microscopes.
  3. Understand how the ability to see cells in more detail under an electron microscope has allowed biologists to have a better understanding of sub-cellular structures.
  4. Be able to use the magnification formula and express answers in standard form.
  5. Be able to understand the size and scale of cells.
  6. Understand how to use estimations to work out the relative size or area of sub-cellular structures.
Please make sure you learn the above topics/points inside out to be fully prepared for your GCSE exam question relating to cells and cell biology.




What is Microscopy?

The microscope is a nearly universal symbol of science, representing our ability to explore the world below the limits of our perception. Microscopy is the technical field of using microscopes to view samples & objects that cannot be seen with the unaided eye, in other words, objects that are not within the resolution range of the normal eye.

As you have understood, the microscope is an instrument that is used to magnify small objects. Some microscopes can be used to observe an object at the cellular level, thereby allowing scientists to see the shapes of a cell, its nucleus and so much more.

So, microscopy is a technique for studying the microscopic world. It is used in biology, medicine, and physics. In microscopy, we use high-powered lenses to magnify objects such as cells and viruses.



What are microscopes?

A microscope is an instrument that is used to magnify small objects. Some microscopes can be used to observe an object at the cellular level, thereby allowing scientists to see the shapes of a cell, its nucleus and so much more.

While the modern microscope has many parts, the most important pieces are its lenses. It is through the microscope’s lenses that the image of an object can be magnified and observed in detail.

Microscopes can be classified into two types: optical microscopes and electron microscopes. Optical microscopes use visible light to view objects whereas electron microscopes use a beam of electrons to produce images of objects.Optical microscopy is the most common type of microscope that we see in science classrooms and laboratories. These are cheap to make, easy to operate, and they generate bright images of small objects like cells or bacteria on slides.



How does it Work?

Light microscopes

A light microscope is an instrument that uses a beam of light to illuminate an object, so that the object can be seen by a human eye or captured on film. The microscope uses two lenses, one for the specimen (the object being examined) and one at the side for illuminating it. The illuminated objects are viewed through this second lens and magnified by the first lens.

Light microscopes work because when you look at any solid object with your eyes alone, your eye captures only a very small part of the wavelengths (colours) that make up all visible light.

This is because your pupil is only about 1mm in diameter, letting through only those wavelengths which are close to the centre of its range - about 400 to 700 nanometers in wavelength.

Light Microscope


‍Electron microscopes

Electron microscopes use electrons instead of light to form an image. Electron microscopes provide higher magnifications and higher resolution images but cannot be used to view living cells. They have a much higher magnification than light microscopes.

The electron beam in an electron microscope is generated by an electron gun and is passed through a high voltage accelerating tube to produce a narrow, intense, well-focused beam of electrons. The electron microscope relies on electromagnetic lenses to magnify the image of the object.

Electron microscopes are used for imaging in many scientific fields such as nanotechnology, quantum physics, biochemistry, and cell biology. They provide higher resolution than light microscopes and because they use electrons rather than photons to form images they are capable of resolving objects as small as 0.1 nm (nanometre) in size (features along this size have been observed).

Electron microscopes let us see much smaller things in more detail, like the internal structure of mitochondria and chloroplasts. They even let us see tinier things like ribosomes and plasmids.

Electron Microscopes

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