Reflection of Light
A mirror sends light back at the same angle.
About this topic
Light reflects from surfaces according to the law of reflection: the angle of incidence equals the angle of reflection, both measured from the normal. A smooth surface gives specular reflection and a clear image, while a rough one scatters light in all directions (diffuse reflection).
In a plane mirror the image is virtual, the same size as the object, upright, laterally reversed and appears as far behind the mirror as the object is in front. Most objects are visible only because they diffusely reflect light into our eyes. Roads are rough on purpose in part so that headlights scatter, and wet roads become more mirror-like and produce glare.
Worked example: to see your full height in a plane mirror, it needs only be half your height, hung with its top halfway between eye and head level, no matter how far you stand. If you walk toward a mirror at 1 m/s, your image approaches you at 2 m/s relative to you.
Applications include periscopes, car mirrors, retroreflectors on bikes and road signs, and the corner reflectors left on the Moon for laser ranging. A misconception is that the mirror swaps left and right; it actually reverses front to back, and left-right reversal is how we interpret it. Another is that dark objects reflect no light, but they absorb most of it.
Key ideas
- Plane mirrors form virtual images
- Diffuse reflection scatters
- Normal line is perpendicular
Quick check
Use cases: where Reflection of Light helps
- Homework: review the key idea behind Reflection of Light before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Reflection of Light without notes.
- Visual learning: play with the interactive lab to see how Reflection of Light changes when you adjust its inputs.
- Teaching a friend: explain Reflection of Light in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Reflection of Light?
A mirror sends light back at the same angle.
What will I learn in Reflection of Light?
Plane mirrors form virtual images. Diffuse reflection scatters. Normal line is perpendicular.
Is Reflection of Light part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Reflection of Light lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Reflection of Light?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.