Reflection of Light By the end of this lesson, you will be able to… Describe the ‘law of reflection’. Explain how to prove the law of reflection. Describe what happens when light is reflected off smooth and rough surfaces. Today’s Activities Why do we see ourselves in mirrors? Drawing ray diagrams Practical – investigating the law of reflection

In groups, discuss and draw a diagram to show how we see a lamp. Eye

So how do we see objects? Draw a diagram to show how we see a ball. Lamp Eye Ball

What happens when a ray of light hits a plane mirror? Reflection What happens when a ray of light hits a plane mirror? Complete the sentence: When a ray of light hits a plane mirror, I predict that …………………..

Drawing ray diagrams Draw and measure the angles of incidence and reflection.

Reflection at a mirror

Reflection ray diagram

How do submariners see what’s on the surface? Use your knowledge of mirrors and reflection.

Using reflection Reflection can be very useful. High-visibility strips are very reflective and make sure that this cyclist gets noticed when there is little light. How does a periscope use reflection? The two plane mirrors must be positioned at 45° from the vertical. Light is reflected at right angles from the top mirror onto the bottom mirror and into the eye of the viewer.

Reflection: summary

Reflection: true or false?

Reflective materials Objects that reflect light well: Have smooth, shiny surfaces and are usually pale colours. Give clear images because they reflect light regularly. Objects that do not reflect light well: Have rough, matt surfaces and are usually dark colours. Give diffuse images (or do not give any images) because they reflect light irregularly. This is called scattering. Photo credit (top): © 2008 Jupiterimages Corporation Photo credit (bottom): © 2008 Jupiterimages Corporation