Reflection of LightCambridge IGCSE Physics: Flashcards
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Define the term 'normal' in the context of reflection of light.
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- Define the term 'normal' in the context of reflection of light.
- The normal is an imaginary line drawn perpendicular (at 90°) to the reflecting surface at the point where the light ray strikes it.
- What is the angle of incidence?
- The angle of incidence is the angle between the incident ray and the normal. It is measured from the normal to the incoming ray.
- Define the angle of reflection.
- The angle of reflection is the angle between the reflected ray and the normal. It is measured from the normal to the outgoing ray.
- State the law of reflection.
- The angle of incidence equals the angle of reflection. Both angles are measured from the normal to the reflecting surface.
- A light ray strikes a plane mirror. If the angle of incidence is 35°, what is the angle of reflection?
- The angle of reflection is 35°. The angle of incidence always equals the angle of reflection.
- Describe the image formed by a plane mirror in terms of size.
- The image formed by a plane mirror is the same size as the object.
- How does the distance of an image from a plane mirror compare to the distance of the object from the mirror?
- The image is formed at the same distance behind the mirror as the object is in front of the mirror.
- What type of image is formed by a plane mirror?
- A virtual image is formed by a plane mirror. The image cannot be projected onto a screen because the light rays do not actually meet; they only appear to meet when extended backwards.
- List three key properties of the image formed by a plane mirror.
- The image is: (1) the same size as the object, (2) the same distance from the mirror as the object, (3) virtual (cannot be projected).
- Explain why the image in a plane mirror is described as virtual.
- The image is virtual because the reflected light rays do not actually converge at the image position. Instead, they appear to diverge from a point behind the mirror when traced backwards.
- When using a plane mirror, how would you measure the angle of incidence?
- Measure the angle between the incident ray and the normal using a protractor. The normal is the perpendicular line to the mirror surface at the point of incidence.
- A light ray hits a plane mirror at an angle of incidence of 0°. What is the angle of reflection and what is special about this ray?
- The angle of reflection is 0°. This ray is special because it hits the mirror along the normal (perpendicular to the surface), so it reflects straight back along the same path.
- Describe how to use a simple construction to locate the position of an image in a plane mirror.
- Draw the normal at the point where a ray strikes the mirror. Construct a ray at an equal angle on the opposite side of the normal. Extend the reflected rays backwards behind the mirror; they intersect at the image position.
- If an object is placed 10 cm in front of a plane mirror, at what distance behind the mirror will its image appear?
- The image will appear 10 cm behind the mirror, as the image distance equals the object distance in a plane mirror.
- What measurements would you take to verify the law of reflection using a plane mirror and light rays?
- Measure the angle of incidence (angle between incident ray and normal) and the angle of reflection (angle between reflected ray and normal) using a protractor. Verify that both angles are equal.