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LearnEdexcel4PH12017 specificationPaper 1P · Paper 1 (core content)Waves

Paper 1P · Module

Waves

4 subtopics≈ 115 min in total

Start the module: General properties of waves Open graphing calculator

General properties of waves
A wave transfers energy from place to place without transferring matter. In a transverse wave the vibrations are at right angles to the direction of travel; in a longitudinal wave they're along it. Every wave obeys $v=f\lambda$ . Waves reflect off barriers, refract when their speed changes, and diffract (spread out) through gaps.
≈ 30 min
Reflection and refraction of light
Light reflects so that the angle of incidence equals the angle of reflection, both measured from the normal. When light enters a denser medium it slows down and bends towards the normal: $n=\dfrac{\sin i}{\sin r}$ . Going the other way, beyond the critical angle all the light reflects back: total internal reflection, used in optical fibres.
≈ 35 min
Electromagnetic spectrum
Electromagnetic waves are transverse waves that all travel at $3.0\times10^8$ m/s in a vacuum. In order of increasing frequency (decreasing wavelength): radio, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays. Each region has its own uses; the highest frequencies carry the most energy and are the most dangerous.
≈ 25 min
Sound
Sound is a longitudinal wave made by vibrating objects: a series of compressions and rarefactions that needs a medium to travel through. Louder sounds have larger amplitude; higher-pitched sounds have higher frequency. Echoes are reflected sound; using distance $=$ speed $\times$ time, and remembering the sound goes there and back, we can measure distances, including with ultrasound.
≈ 25 min