American Board of Opticianry (ABO) Practice Test 2026 - Free ABO Practice Questions and Study Guide

Question: 1 / 400

What is the speed of light in air?

186,000 miles per second

The speed of light in air is approximately 186,000 miles per second. This value is derived from the speed of light in a vacuum, which is roughly 299,792 kilometers per second (or about 300,000 kilometers per second), and when light travels through air, its speed is slightly reduced due to the refractive index of air. However, this reduction is minimal, so for practical purposes, the speed of light is often approximated as 186,000 miles per second when discussing its behavior in air.

Other options do not relate directly to the measurement of the speed of light. One meter is a unit of distance, not a measure of speed. One diopter prism refers to a unit related to the bending of light, but does not specify speed. Refraction is a phenomenon that describes how light changes direction when moving from one medium to another, not a measurement of speed itself. Thus, stating that the speed of light in air is 186,000 miles per second accurately captures the scientific consensus on this topic.

Get further explanation with Examzify DeepDiveBeta

One meter

One diopter prism

Refraction

Next Question

Report this question

Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy