OCR · A-Level · Physics
Course version: H556 · Version from Sept 2015
(i) reflection, refraction, polarisation and diffraction of all waves
Full specification wording
Wave motion: (i) reflection, refraction, polarisation and diffraction of all waves
Waves exhibit several key behaviours: reflection, refraction, diffraction, and polarisation.
Checked against the OCR H556 specification (opens in a new tab) on .
- Point 7 of 11
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Waves exhibit several key behaviours: reflection, refraction, diffraction, and polarisation. Reflection is the change of direction at a boundary, where the angle of incidence equals the angle of reflection (measured from the normal). Refraction occurs when a wave changes speed upon entering a new medium, altering its wavelength and direction while frequency remains constant. Diffraction is the spreading of a wave as it passes through a gap or around an obstacle, being most pronounced when the gap width is comparable to the wavelength. While reflection, refraction, and diffraction apply to all waves, polarisation—which restricts oscillations to a single plane—is exclusively a property of transverse waves. Longitudinal waves, such as sound, cannot be polarised.
What earns the marks
- States that reflection occurs at a boundary with the angle of incidence equal to the angle of reflection, both measured from the normal.
- Explains refraction as a change in wave speed at a boundary causing a change in direction and wavelength, with frequency unchanged.
- Describes diffraction as the spreading of a wave through a gap or around an obstacle, which is most pronounced when the gap width is similar to the wavelength.
- Identifies polarisation as restricting oscillations to a single plane and explicitly notes it applies only to transverse waves.
Common mistakes and how to put them right
Stating that all waves can be polarised.
Put it right: Polarisation is only possible for transverse waves; longitudinal waves cannot be polarised.
Measuring angles of incidence and reflection from the boundary.
Put it right: These angles must always be measured from the normal.
Assuming frequency changes during refraction.
Put it right: Frequency remains constant; it is the wave speed and wavelength that change.
Exam tips
- Always draw the normal as a dashed line at a boundary and mark angles from it.
- When explaining refraction, explicitly state that the frequency of the wave remains unchanged.
- To maximise marks on diffraction questions, refer to the ratio of gap width to wavelength.
Try the lesson
The start of the Wave motion: (i) reflection, refraction, polarisation and diffraction of all waves lesson, made from checked teaching notes for this specification point.
Listen
Waves exhibit several key behaviours: reflection, refraction, diffraction, and polarisation. Reflection is the change of direction at a boundary, where the angle of incidence equals the angle of reflection (measured from the normal). Refraction occurs when a wave changes speed upon entering a new medium, altering its wavelength and direction while frequency remains constant. Diffraction is the spreading of a wave as it passes through a gap or around an obstacle, being most pronounced when the gap width is comparable to the wavelength. While reflection, refraction, and diffraction apply to all waves, polarisation—which restricts oscillations to a single plane—is exclusively a property of transverse waves. Longitudinal waves, such as sound, cannot be polarised. A strong answer earns marks for these points. States that reflection occurs at a boundary with the angle of incidence equal to the angle of reflection, both measured from the normal. Explains refraction as a change in wave speed at a boundary causing a change in direction and wavelength, with frequency unchanged. Describes diffraction as the spreading of a wave through a gap or around an obstacle, which is most pronounced when the gap width is similar to the wavelength. Identifies polarisation as restricting oscillations to a single plane and explicitly notes it applies only to transverse waves. A common slip: Stating that all waves can be polarised. Instead, polarisation is only possible for transverse waves; longitudinal waves cannot be polarised. Exam tip: Always draw the normal as a dashed line at a boundary and mark angles from it.
See it
Key words
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Reflection at boundaries
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Refraction and wave speed
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Diffraction and gap-to-wavelength ratio
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Polarisation of transverse waves
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See every definition
- Reflection at boundaries
- The change of direction at a boundary, where the angle of incidence equals the angle of reflection, both measured from the normal.
- Refraction and wave speed
- A change in wave speed upon entering a new medium, altering wavelength and direction while frequency remains constant.
- Diffraction and gap-to-wavelength ratio
- The spreading of a wave as it passes through a gap or around an obstacle, most pronounced when the gap width is comparable to the wavelength.
- Polarisation of transverse waves
- Restricting oscillations to a single plane, a property exclusively of transverse waves, so longitudinal waves cannot be polarised.
Label the diagram
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