Just another WordPress site

what is the function of objective lenses in a microscope?


WordNet – Cite This Source – Share This objective lensnoun the lens or system, used to view any object at different magnifications , The objective lens focuses the light entering a refracting telescope.

hey magnify the image of the object being observed. A 0.1mm object will appear to be 1mm long with the 10X objective, 4mm long with the 40X objective and 10mm long with the 100X objective. They therefore enable you to see finer details of the object.


Most microscopes have four objective lenses, and each provides a varying level of magnification. The shortest objective possesses the least power (4X), and is called the scanning objective. It is followed by the low power objective (10X) and the high power objective or “high-dry” objective (40X). The longest objective, which is also the strongest, is the oil immersion objective (100X). The maximum magnification potential of an objective lense is typically determined by its distance from the image plane and the specimen that’s being observed.

The objective lens gathers light from a very small area and a very close range of distances the thickness of water on glass slide + (under) small thin square cover glass usually.

Sometimes no liquid is there, nor cover glass square, but dried, stained materials may be viewed, with ‘oil immersion’ lens at high magnifications.

such as Gram stain films on glass slide, stained smears of biological materials, drop of blood spread as thin film, dried and stained, usually Wright’s stain. Wright’s stain blood view
Basics of Wright’s stain

There are now a large variety of microscopes, many binocular, and not all do very high magnification, I only described common medical ones. Lenses with less magnification do not require being so close to specimen as those with higher. Often there is a choice of three different, rotating lenses.

20X Objective lens that screws onto microscope

This one is adequate for much routine medical lab or biology work for a student or even a med tech

Good online biology reference

Good place to see several microscopes types of varying price, low to high cost

More helpful lucid concise explanation of compound microscope

Use a light — little girl gentle — touch when winding down high magnification objective lens so that you do not damage or break it. Newbie Gargantua Junior types might actually do that. STOP when you encounter resistance…

Geologists and others use varying types, often lower power stereo, too much to detail here.

Spiffy microscope and specs Advanced Compound Microscope with Tablet (M10T-BTW1-MP) Compound means two lenses, eyepiece lens and objective lens, basically.

Microscope Guide — be sure to scroll down and read, see the illustrations

Microscope SAFETY:

Never startle or surprise a person engrossed in microscope viewing
NEVER surprise touch or slap on back someone peering through microscope
The foregoing are not merely polite, but avoid SEVERE injury to eyes
Do NOT buy higher price microscope than you need, they are attractive to savvy thief if expensive

What is the Objective Lens?

The objective lens in a microscope is the lens that is closest to the specimen being magnified. Although there are many lenses in the microscope, each of which performs a different type of function, it is the objective lens that contributes the most to enhancing the detail of the specimen. Most microscopes have three or four objective lenses. Each objective lens provides a different level of magnification. The longest lens possesses the greatest magnification power. Since the objective lens is closest to the specimen, it is the farthest from the eye of the observer and provides the greatest magnification.

Objective Lens Types

The objective lens strengths found in most microscopes are the 4x, 10x, 40x and 100x. To calculate the actual magnification provided by each type of objective lens, simply multiply the number before the x by ten. Thus a 4x lens actually shows an object at 40 times its natural size. 10x lenses show an object at 100 times, a 40x at 400 times, and a 100x at 1,000 times magnification.

How It Works

The magnification potential of the objective lens is determined by the ratio between its distance from both the specimen and the image plane. The image plane is where we actually observe the magnified image. For most standard microscopes the image plane is in the eye pieces through which you look. More sophisticated microscopic equipment may also feature a projector which casts the image onto a separate surface. Here it is the focal point from which the image is projected that constitutes the image plane, rather than the eye pieces.

Related Items