Summary

Unit 1 in Brief

• Physics studies nature across an enormous range of scales, from sub-atomic particles to galaxies, organised broadly into macroscopic and microscopic domains.
• A physical law is expected to be universal and time-invariant; physics has repeatedly turned such laws into technologies (electromagnetism → electricity; semiconductor physics → computing) that have reshaped society.
• Measurement compares an unknown quantity against a fixed unit; the world has agreed on one coherent system of units, the SI system, built from seven base units, now defined using fixed constants of nature rather than physical artefacts.
• Length, mass and time are each measured with instruments matched to the scale involved — from a metre scale to a caesium atomic clock.
• Accuracy (closeness to the true value) and precision (repeatability) are different properties of a measurement; both systematic and random errors limit them, and are handled differently.
• Significant figures and rounding-off / order-of-magnitude rules record and communicate exactly how precisely a value is actually known. …