Topic 5 of 8 · Form 3
Waves: properties, light, sound and the electromagnetic spectrum
Transverse and longitudinal waves; amplitude, wavelength, frequency, period; v = fλ; reflection, refraction and diffraction (ripple tank).
Notes for this topic 1 file, in order
Create a free account to download PDFs.
General wave properties
Transverse and longitudinal waves; amplitude, wavelength, frequency, period; v = fλ; reflection, refraction and diffraction (ripple tank).
Light
- Reflection: angle of incidence = angle of reflection; plane mirror images.
- Refraction: n = sin i / sin r; n = c/v; critical angle sin c = 1/n; total internal reflection (optical fibres, prisms).
- Thin converging lenses: principal focus, real and virtual images, ray diagrams; magnifying glass.
- Dispersion of white light into a spectrum.
Worked example: Light passes from air into glass (n = 1.5) at 40° incidence. Find the angle of refraction.
sin r = sin 40° ÷ 1.5 = 0.4285 → r = 25.4°
Electromagnetic spectrum
Radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays; all travel at 3.0 × 10⁸ m/s in a vacuum; uses and hazards.
Sound
Longitudinal waves needing a medium; compressions and rarefactions; speed in air about 330–340 m/s; echoes; ultrasound (above 20 kHz) used in medical scanning and sonar.
Check yourself
- Find the critical angle for glass with n = 1.5.
- Which part of the EM spectrum is used for satellite TV?
- A sound wave has frequency 500 Hz and wavelength 0.68 m. Find its speed.
Show answers
- sin c = 1/1.5 → c = 41.8°
- Microwaves.
- 340 m/s
Questions about this topic (0)
No questions about this topic yet.
Sign in or create a free account to join in.