Study sheet: Microscopes and Medical Imaging

📋 Course Outline

1. Light Microscope Principles
2. Magnification and Image Appearance
3. Electron Microscope Types
4. Medical Imaging Technologies

📖 1. Light Microscope Principles

🔑 Key Concepts & Definitions

• Light microscope : uses light and glass lenses to magnify objects, allows light to pass through the specimen, and can be used to view living or preserved specimens
• Phase-contrast microscope : is a light microscope that enhances contrast and is useful for examining living, unstained cells

📝 Essential Points

• Stains are often used to make specimens easier to view with a light microscope.

• Light microscopes provide magnification up to 1500 times.

💡 Memory Hook

Light microscopes use light and glass lenses, whereas electron microscopes use electrons.

📖 2. Magnification and Image Appearance

★ Must-know

📐 Formula — Total magnification equals the magnification of the ocular lens multiplied by the magnification of the objective lens: $M = M_{ocular} \times M_{objective}$.

📐 Formula — Magnification equals drawing size divided by actual size: $M = \frac{I}{A}$.

• The metric scale relationships are 1 meter = 100 centimeters = 1000 millimeters = 1 × 10^6 micrometers = 1 × 10^9 nanometers.

• Objects viewed through a light microscope appear upside-down and backward, and their apparent movement is opposite to their actual movement.

Further detail

• Actual size equals drawing size divided by magnification, and drawing size equals magnification multiplied by actual size.

💡 Memory Hook

Ocular × objective → magnification; drawing ÷ actual → magnification.

📖 3. Electron Microscope Types

🔑 Key Concepts & Definitions

• Scanning electron microscope : uses electrons that bounce off a specimen; a computer detects and interprets them to form a three-dimensional image of the specimen’s surface
• Transmission electron microscope : uses electrons that pass through a specimen to produce a two-dimensional image of a thin specimen slice

★ Must-know

• An SEM cannot be used to study a living specimen but can magnify a specimen more than 100,000 times.

Further detail

• A TEM cannot be used to study living specimens but can clearly magnify specimens more than 100,000 times.

💡 Memory Hook

SEM shows the surface in 3D, whereas TEM shows a thin section in 2D.

📖 4. Medical Imaging Technologies

🔑 Key Concepts & Definitions

• Magnetic resonance imaging : uses a strong magnetic field to produce a cross-sectional image of a part of the body

★ Must-know

• X-rays pass through soft tissues such as skin and muscle but are absorbed by bones and teeth.

📌 X-ray images are very useful for examining the skeleton but are not as useful for examining soft tissues such as ligaments, cartilage, or the brain.

Further detail

• A series of MRI images can be put together to provide a complete view of all the tissues in the imaged area.

• Imaging technology is used in medicine to examine structures such as bones, teeth, soft tissues, and regions of the body.

💡 Memory Hook

X-rays reveal dense bones, whereas MRI reveals soft tissues.

📊 Synthesis Tables

Microscope Comparison

Instrument	Signal and interaction	Image	Living specimen
Light microscope	Light passes through the specimen	Magnified optical image	Can be used
SEM	Electrons bounce off the specimen	Three-dimensional surface image	Cannot be used
TEM	Electrons pass through the specimen	Two-dimensional thin-section image	Cannot be used