Presentation on theme: "Reflection 3.2 (a) Reflection of light Core"— Presentation transcript:
1Reflection 3.2 (a) Reflection of light Core • Describe the formation, and give the characteristics, of an optical image by a plane mirror• Use the law angle of incidence = angle of reflectionSupplement• Perform simple constructions, measurements and calculations
2Objectives Recall that light travels in straight lines. Draw accurate ray diagrams.Describe how we see objects.Define the words opaque and transparent.Describe the images formed in a plane mirror.Recall how the angle of incidence and angle of reflection are related for a plane mirror.Describe the differences between convex and concave mirrors.
3Light raysA light ray is a narrow beam of light. When drawing light diagrams always…..1. Use a ruler.2. Add an arrow to show the direction the light ray is travelling in.
4How does light travel?1) Fill a clear glass trough or empty fish tank with smoke.2) Shine rays of light through the tank and describe what you see.
5Light travels in straight lines Your experiment shows that light travels in straight lines.What every day consequences do you think this fact has?You can not see around corners.Shadows are formed in the area behind an object where light can not reach.
6Seeing objects How do we see an object? There are two ways we see objects…..Do we see all objects in the same way?We see some objects because they are light sources.We see some objects by reflected light.
7Objects seen by reflected light Seeing objectsLight sourcesObjects seen by reflected lightSunJupiterFireflyMoonLight bulbBookLight bulbSunJupiterBookFireflyMoon
8Light sourcesHow do light rays from the Sun and other light sources reach our eye?They travel in a straight line directly into our eye.
9Reflected lightHow do light rays from a book and other such objects reach our eye?Light from the Sun or another light source strikes the book and some of the light is reflected into our eye.
10Opaque and transparent materials Use a textbook or other source to find out what the words opaque and transparent mean.Opaque materials do not let light though.Transparent materials do let light through.
11There are two types of m____. F__ mirrors and c____ mirrors. ReflectionsThere are two types of m____. F__ mirrors and c____ mirrors.Flat mirrors are known as p___ mirrors.If a mirror curves in then it is a c_____ mirror, if it curves out it is a c____ mirror.irrorslaturvedlaneoncaveonvex
12Plane mirrorsWrite out the letters of the alphabet down one side of a piece of paper, then next to the letter draw what the letter would look like as seen in a mirror.What do you predict the letter ‘L’ would look like in a mirror?What do you predict the letter ‘P’ would look like in a mirror?
13Right and left What happens to writing in a mirror? The writing in a mirror is laterally inverted or back to front.If you are wearing a T-shirt with some writing on and wave your right hand what will your image appear like in a mirror?The writing on your T-shirt will be back to front and your image will be waving it’s left hand.
14Ambulance Ambulance Rear-view mirrors Imagine you are driving along in your car……Ambulance…and then you look up and see the following in your mirror…..Ambulance…with your knowledge of mirrors how must the writing be written on the vehicle?
15Reading in Mirrors In small groups, take it in turns to read the list of words on the next slide with your back to the screen using a mirror. You can only move on to the next word when you read the first word correctly. Put your results in a table like this:
16Dog Man Ball Bat Bike Ants Park Fins Pink Litter Sandy Shark WordsDog Man BallBat Bike AntsPark Fins PinkLitter Sandy SharkNo Cheating
17Results A) Who read the words in the quickest time? B) Plot a bar chart of you r results like:C) What was the average time taken in your group?
18Image size and distance For a plane mirror how does the size of the image and the image distance from the mirror relate to the original object?ImageObjectImage size and object size are the same.The image distance is the same as the object distance from the mirror.
19Investigating reflection Apparatus:Power packRay boxSlitConcave mirrorProtractorRulerThe ray boxwill get veryhot, be carefulwhen handling it.
20Investigating reflection 1. Place the concave mirror on a piece of paper.2. Draw a line along the front of the mirror.3. Shine rays of light at varying angles to the normal and record the position of the incident and reflected raysIncident angle iIncident ray4. Draw a tangent to the mirror where the ray hits.Reflected angle r5. Draw a normal to the mirror (at right angles to the previous line).Reflected ray6. Measure the incident angles and the reflected angles for each ray. Record your results in a table.
21Angle of incidence = Angle of reflection Resultsi/°r/°3045708530457085Angle of incidence = Angle of reflectionWhat do you notice? Is there a pattern?
22Using plane mirrorsBy positioning two plane mirrors at 45° to each other at either end of a tube we can make a _________.periscopePeriscopes are used in __________.submarines
23Reflection : Curved mirrors Concave reflectors are used to focus signals from distant satellites.Convex reflectors are used to widen the field of view.
24Which of the following is not a light source? The SunA starTraffic lightsA book
25Which of the following is not seen by reflected light? Your handJupiterLight bulbThe Moon
26Which of the following is the most opaque? MilkSea waterAirDrinking water
27What do we call the area behind an object where light can not reach? TransparentShadowOpaqueOutline
28Which statement below is untrue for the image in a plane mirror? It is laterally invertedIt is realIt is same size as the objectIt is the same distance from the mirror as the object
29Objectives Recall that light travels in straight lines. Draw accurate ray diagrams.Describe how we see objects.Define the words opaque and transparent.Describe the images formed in a plane mirror.Recall how the angle of incidence and angle of reflection are related for a plane mirror.
30as far behind the mirror as the object is in front, =What I should know:The law of reflection:the angle = the angleof incidence of reflectionA periscope uses 2 mirrors, set at 45° to the horizontal.The image in a plane mirror is:as far behind the mirror as the object is in front,the line joining the image to the object is at 90° to the mirror,a virtual image (no light rays go through it),the same size as the object,laterally inverted.What I should be able to do: Carry out an experiment to test the law of reflection. Draw a diagram of a periscope and explain how it works. Describe an experiment to find out the position of an image in a plane mirror. Understand a ray diagram which shows 2 light rays reflected off a mirror and into an eye.