透過

• Reading: とうか
• Romaji: tōka
• Kanji breakdown: 透 (tō/su-) — transparent, pass through; 過 (ka/su-gi) — pass, exceed
• Pronunciation: /toː.ka/

Meaning

Transmission; permeation; the passage of light, radiation, or particles through a medium or barrier without being absorbed or reflected.

A noun (also suru-verb) used in optics, radiology, biology, and materials science. 透過率 (transmittance) quantifies how much radiation passes through a material. In biology, 透過 describes the movement of substances across membranes. X線透過 (X-ray transmission) is an everyday medical application. Contrasted with 反射 (reflection) and 吸収 (absorption).

Examples

1. X線は軟組織を透過するが骨では吸収されるため、骨折の診断に使われる。 X-rays pass through soft tissue but are absorbed by bone, which is why they are used to diagnose fractures.
2. この素材の光透過率を測定したところ、可視光の約90パーセントを通過させた。 When the light transmittance of this material was measured, it was found to pass approximately 90 percent of visible light.
3. イオンチャネルを通じた細胞膜の透過を制御する仕組みを解析した。 The mechanism controlling permeation through the cell membrane via ion channels was analyzed.

Usage Guide

Context: optics, radiology, biology, materials science

Tone: neutral

Origin & History

Compound of 透 (tō — transparent, pass through) and 過 (ka — pass, exceed). Together they convey the idea of passing through something completely.

Cultural Context

Era: Modern

Generation: Students and professionals

Social background: Technical