Optical instruments – microscope, telescope, camera

Optical instruments are tools that help us see things we cannot see with our eyes. They expand our ability to see things, from tiny cells to distant galaxies. In this article, we will focus on three common optical instruments: microscopes, telescopes, and cameras.

Light and optics are the basis of these devices. Light travels in waves, and when it interacts with different materials, it bends, reflects, and splits into different colors. Optics is the study of how light behaves and how it can be manipulated to create these devices.

Microscope

Microscopes are optical instruments designed to magnify tiny objects that are too small to be seen with the naked eye. They are widely used in fields such as biology, medicine, and materials science.

Parts of a microscope

• Eyepiece : The part you look through, usually has a 10x lens.
• Objective lenses : These are found on a rotating nosepiece, with varying magnifications (e.g., 4x, 10x, 40x, 100x).
• Stage : The platform where you place the slide.
• Light source : Lights the slide from below.
• Focus knob : Adjusts the focus to make the image sharp.

How Microscopes Work

There are two main lenses used to magnify objects in a microscope: the eyepiece lens and the objective lens. The total magnification is obtained by multiplying the magnification of these two lenses.

Total Magnification = Eyepiece Magnification × Objective Lens Magnification

For example, if the eyepiece lens is 10x and the objective lens is 40x, the total magnification will be:

Total Magnification = 10× × 40× = 400×

Example of a light path in a microscope

In the above visual example, light passes through the object, converges through the objective lens (the circle in the scene), and then gets magnified through the eyepiece to be seen by our eyes.

Telescope

Telescopes allow us to observe distant objects, such as stars, planets and galaxies. They are essential tools in astronomy.

Types of telescopes

• Refracting telescopes : use lenses to bend and focus light.
• Reflecting telescopes : use a mirror to gather and focus light.

Working of Refracting Telescope

Refracting telescopes use a large lens called the objective lens to collect light. This lens focuses the light onto a smaller lens, known as the eyepiece, allowing us to see a magnified image of distant objects.

Example of the light path in a refracting telescope

In the above view, the light path enters the telescope, bends through the objective lens, converges to a point, and finally passes through the eyepiece lens to form an image.

Reflecting telescope

Reflecting telescopes use mirrors to collect light. The main mirror, called the primary mirror, reflects light onto a smaller mirror, which then directs the light into the eyepiece lens.

Camera

Cameras capture an image of an object by focusing light onto a light-sensitive surface. They are used in photography and videography to record moments visually.

Parts of the Camera

• Lens : Focuses light onto the sensor or film.
• Aperture : A hole through which light enters; controls the amount of light.
• Shutter : Opens and closes to allow light to fall on the sensor or film for a certain period of time.
• Sensor or film : The surface that captures the image.

How the camera works

Light enters through the lens and is focused onto the sensor or film. The aperture determines how much light enters, while the shutter speed determines how long the sensor or film is exposed to this light.

Exposure = Aperture × Shutter Speed

For a good photo you need the right combination of aperture and shutter speed.

Example of image formation in a camera

In the scene, light rays pass through the camera lens and are focused onto the image sensor or film, forming a picture.

Optical instruments extend our vision beyond its natural limits by using the principles of light and optics. Microscopes magnify tiny details, telescopes let us observe distant worlds, and cameras capture moments and details in time. By understanding the basic principles and functions of these instruments, we can explore and appreciate both the microcosm and macrocosm that the universe has to offer.

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