Reflection
Overview
Look at the front of an ambulance in your mirror and the word across its bonnet suddenly makes sense. It was painted back to front on purpose, because the only driver who needs to read it is the one looking at it through a piece of silvered glass. Somebody in a paint shop had to know, in advance and exactly, what a mirror does to a shape. They were not guessing. Reflection is one of the most precisely predictable things in the whole of physics, and the rule behind it fits into nine words.
This lesson turns that rule into a skill. You will learn where the normal is drawn and why every angle in this topic is measured from it rather than from the shiny surface itself, which is where most of the marks on this topic are quietly thrown away. You will then learn to build a ray diagram: to place the image behind the mirror by construction, find the exact point where the light bounces on its way to somebody's eye, and follow how that path shifts when the object moves, when the eye moves, or when the mirror itself is turned. By the end you will be able to say why the letters on the ambulance are reversed left to right and not top to bottom, which is a question far more people get wrong than get right.
Objectives
- When waves are reflected the angle of incidence is equal to the angle of reflection.
- The normal is a construction line perpendicular to the reflecting surface at the point of incidence.
- The image produced in a plane mirror is virtual, upright and laterally inverted. Students will be expected to be able to construct ray diagrams to represent the changing path of reflected rays.
Mind map
This topic is mapped out so you can see how the ideas connect.
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Lesson Note
Complete Note Available on the Green Bridge App
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Lesson Evaluation
Congratulations on completing the lesson on Reflection. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- A ray of light strikes a plane mirror. The angle between the incident ray and the surface of the mirror is 30 degrees. What is the angle of reflection? A. 15 degrees B. 30 degrees C. 60 degrees D. 120 degrees Answer: C
- What is the normal in a reflection diagram? A. A ray of light travelling along the reflecting surface B. A construction line drawn perpendicular to the reflecting surface at the point of incidence C. The reflected ray D. A line joining the object to the edge of the mirror Answer: B
- Which set correctly describes the image formed in a plane mirror? A. Real, upright and laterally inverted B. Virtual, upright and laterally inverted C. Virtual, upside down and the same way round left to right D. Real, upside down and magnified Answer: B
- An object is placed 5.0 cm in front of a plane mirror. What is the distance between the object and its image? A. 2.5 cm B. 5.0 cm C. 10.0 cm D. 25 cm Answer: C
- A plane mirror is rotated through 8 degrees while the incident ray is kept fixed. Through what angle does the reflected ray turn? A. 4 degrees B. 8 degrees C. 16 degrees D. 32 degrees Answer: C
Work through these questions in the app
Work through these questions in the app
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Practice Mock Questions
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