Read Light: Use Rays, Normals and Straight Lines
Light normally travels in straight lines. Draw that path first, then apply reflection or an eclipse alignment.
Reflection, shadows and eclipses is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Keep the Sun, Earth and Moon positions separate
Position and motion create the observed pattern
Rotation explains day and night; revolution changes Earth’s position around the Sun. Eclipses and phases depend on the viewing geometry.
Measure angles from the normal
The angle between an incident and reflected ray is 2i.
Decide visibility with a ray
To see an object in a plane mirror, a ray from the object must reflect into the eye. Extend the reflected ray behind the mirror to locate its virtual image.
Keep shadow and eclipse ideas separate
A shadow is the dark region where an opaque object blocks light. A solar eclipse occurs when the Moon’s shadow falls on Earth; a lunar eclipse occurs when Earth lies between the Sun and Moon.
OlympIQ exam lens
- ✓Draw the normal before measuring an angle.
- ✓Trace one valid object–mirror–eye ray.
- ✓Identify which body casts a shadow in an eclipse.
The colour of a shadow does not depend on the object’s colour. It depends on light being blocked.
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