- Define and explain Reflection and Refraction in your own words
- Use key terms such as refraction accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Reflection and Refraction: explaining how waves bounce off surfaces and bend at boundaries.
Explaining how waves bounce off surfaces and bend at boundaries.
Key ideas
Waves carry energy without carrying matter
In a transverse wave (like light or a rope wave) the vibrations are at right angles to the direction of travel; in a longitudinal wave (like sound) they are parallel, forming compressions and rarefactions. The medium oscillates but does not travel with the wave — only energy moves onwards, which is why a floating duck bobs up and down as ripples pass.
Wave speed links frequency and wavelength
v = f × λ: speed equals frequency times wavelength. Higher frequency means more waves per second, so for a fixed speed the wavelength must shrink. Rearranging gives f = v ÷ λ and λ = v ÷ f — learn all three forms.
Key term — refraction: The bending of a wave as it crosses into a material where its speed changes.
A ray of light bends as it enters glass from air. Name the effect and explain why it happens.
Refraction — light slows down in glass, and the change in speed at the boundary bends the ray.
Answer: Refraction — light slows down in glass, and the change in speed at the boundary bends the ray.
- Thinking different EM waves travel at different speeds In a vacuum every EM wave travels at 3 × 10⁸ m/s — speed does not depend on wavelength.
- Saying the medium moves along with the wave Particles oscillate in place; only energy is transferred along the wave.
Practice
Microwaves: cooking food, mobile phone and satellite communication. Infrared: overexposure can cause skin burns.
50 × 4 = 200 m/s.
Longitudinal — air particles vibrate parallel to the direction the sound travels, in compressions and rarefactions.
Blue light — with speed constant, shorter wavelength means higher frequency.
Quick check
Which of these best defines "refraction"?
An EM wave has wavelength 0.5 m. Calculate its frequency (c = 3 × 10⁸ m/s).
- Reflection and Refraction: explaining how waves bounce off surfaces and bend at boundaries.
- Waves carry energy without carrying matter: In a transverse wave (like light or a rope wave) the vibrations are at right angles to the direction of travel; in a longitudinal wave (like sound) they are parallel, forming compressions and rarefactions.
- wavelength: The distance between two matching points on neighbouring waves, e.g.
- Watch out for: thinking different EM waves travel at different speeds