AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Students should be able to construct ray diagrams to illustrate the…
Full specification wording
Reflection of waves (physics only): Students should be able to construct ray diagrams to illustrate the reflection of a wave at a surface.
A reflection ray diagram is a ruled construction, not a sketch.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 3 of 4
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A reflection ray diagram is a ruled construction, not a sketch. Mark the point where the incident ray strikes the mirror, then draw the normal there as a dashed line at 90° to the mirror surface. Measure the angle of incidence between the incident ray and the normal with a protractor, measure the same angle on the other side of the normal, and draw the reflected ray as a straight ruled line from that same point. Arrows must be drawn on the rays to show the direction of travel. To find an image in a plane mirror, continue the reflected rays backwards as dotted construction lines; where they appear to meet behind the mirror is the virtual image, as far behind the mirror as the object is in front. Marks are given for the normal at 90°, ruled lines, equal angles and correct arrows.
What earns the marks
- A normal drawn at 90° at the exact point where the incident ray strikes the mirror.
- The reflected ray drawn as a straight line with a ruler.
- An angle of reflection equal to the angle of incidence, within the tolerance given.
- Adding correct direction arrows to the incident and reflected rays.
Common mistakes and how to put them right
Drawing the normal along the mirror surface instead of perpendicular to it.
Drawing the reflected ray from a different point on the mirror to the one the incident ray hits.
Sketching the rays freehand so the angles fall outside the examiner tolerance.
Forgetting to add arrows to the rays to indicate the direction of wave travel.
Exam tips
- Take a sharp pencil, a ruler and a protractor into the exam; reflection diagrams are marked on measured angles.
- Label the angle of incidence i and the angle of reflection r so the examiner can see you measured from the normal.
- Always include arrows on your rays, as marks are often awarded for showing the correct direction of travel.
Try the lesson
The start of the Reflection of waves (physics only): Students should be able to construct ray diagrams to illustrate the reflection of a wave at a surface. lesson, made from checked teaching notes for this specification point.
Have a go first
On a ray diagram showing a wave reflecting off a flat surface, what is the name of the line drawn at 90° to the surface at the point where the ray hits it?
Listen
A reflection ray diagram is a ruled construction, not a sketch. Mark the point where the incident ray strikes the mirror, then draw the normal there as a dashed line at 90° to the mirror surface. Measure the angle of incidence between the incident ray and the normal with a protractor, measure the same angle on the other side of the normal, and draw the reflected ray as a straight ruled line from that same point. Arrows must be drawn on the rays to show the direction of travel. To find an image in a plane mirror, continue the reflected rays backwards as dotted construction lines; where they appear to meet behind the mirror is the virtual image, as far behind the mirror as the object is in front. Marks are given for the normal at 90°, ruled lines, equal angles and correct arrows. A strong answer earns marks for these points. a normal drawn at 90° at the exact point where the incident ray strikes the mirror. the reflected ray drawn as a straight line with a ruler. an angle of reflection equal to the angle of incidence, within the tolerance given. adding correct direction arrows to the incident and reflected rays. Exam tip: Take a sharp pencil, a ruler and a protractor into the exam; reflection diagrams are marked on measured angles.
Key words
Say what each word means before you turn the card.
normal at 90°
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equal angles
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virtual image
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See every definition
- normal at 90°
- A dashed line drawn at the point where the incident ray strikes the mirror, at 90° to the mirror surface.
- equal angles
- The angle of reflection is equal to the angle of incidence, both measured from the normal.
- virtual image
- Where the reflected rays appear to meet behind the mirror, as far behind the mirror as the object is in front.
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