# Optics Reflection, Refraction & Total Internal Reflection

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Optics Reflection, Refraction & Total Internal Reflection. Revision on Reflection. Quiz No 1 - PowerPoint PPT Presentation

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• OpticsReflection, Refraction & Total Internal Reflection

• Revision on ReflectionQuiz No 1 Six students are arranged in front of a mirror. Their positions are shown below. The image of each student is also drawn on the diagram. Make the appropriate line of sight constructions to determine which students each individual student can see.

• Ans Al can see Ed and FredBo can see Ed, and FredCy can see Cy, Di, Ed, and FredDi can see Cy, Di, and Ed,Ed can see Al, Bo, Cy, Di, and EdFred can see Bo, Cy, Di, and Ed

• Quiz No. 2 A man 2.0 m tall wishes to see his full length in a plane mirror. The minimum length of mirror that he must buy is A 2.5 m B 2.0 m C 1.25 m D 1.0 m

• AnsD. 1:2 ratio between portion of mirror required to view the image and the height of the object is observed.

• Whats Wrong Here?Can you spot 3 subtle distortions of reality in this painting? (Painting: A Bar at the Folies-Bergere)

• 3 Subtle Distortions1)Note the bottles at the left. Manet painted their reflections in the mirror but misplaced them, painting them farther toward the front of the bar than they should be.2)Note the reflection of the women. Since your view is from directly in front of the woman, her reflection should be behind her, with only a little of it ( if any) visible to you. Yet Manet painted her reflection well off to the right.3)Note the reflection of the man facing her. He must be you! Because reflection shows that he is directly in front of the woman, and thus he must be the viewer of the painter. You are looking into Manets work and seeing your reflection well off to your right. The effect is errie because it is not what we expect from a painting or from a mirror.

• Refraction

• Magic or Physics?

• Revision on RefractionQuiz No. 2

When light passes from an optically denser medium into an optically less dense medium, it will bend ______________ the normal.

When light passes from a medium with a low refractive index into a medium with high refractive index, it will bend ____________ the normal.

• Quiz No. 3Complete the diagram til the light ray enters air again.Label thenormal / incident ray / refracted ray / angle of incidence / angle of refraction

• Quiz No. 4Indicate on the diagram the approximate location where Arthur observes the fish to be. Must Arthur aim above or below where the fish appears to be in order to strike the fish?

• The story of the Archer Fish

• If you were that disabled Archer FishIf you are an Archer Fish, born without the natural talent of solving the physics of refraction, what would you do to compensate your lack of talents? Hintthink physics.you do have a way out

• Just Apply Power of Physics!

• Optical DensityLike any wave, the speed of a light wave is dependent upon the properties of the medium. In the case of an electromagnetic wave, the speed of the wave depends upon the optical density of that material. The optical density of a medium is not the same as its physical density. The more optically dense which a material is, the slower that a wave will move through the material.

• Refractive Index ()One indicator of the optical density of a material is the refractive index () of the material. It is a number which indicates the number of times slower that a light wave would be in that material than it is in a vacuum. A vacuum is given an value of 1.0000.

• Refractive IndexMaterialIndex of RefractionVacuum 1.0000
• Snells LawThere exist a relationship between the angle of incidence and refraction and the refractive indexes of the two mediums:

• Quiz No. 5Determine the angle of refraction for the following problems.

• AnsA : 53.9oB: 28.4o

We usually leave angles to 1 d.p

• Quiz No. 6Perform the necessary calculations at each boundary in order to trace the path of the light ray through the following series of layers. Show all the calculated angles.

• Ansair - flint glass: 18 degrees flint glass - water: 22 degreeswater - diamond: 12 degrees diamond - zirconium: 13 degreescubic zirconium - air: 30 degrees

• Quiz No. 7A ray of light is traveling through air (n = 1.00) towards a lucite block (n = 1.40) in the shape of a 30-60-90 triangle. Trace the path of the light ray through the lucite block shown in the diagram below.

• Ans

• Refractive Index

• Absolute Refractive Index

• Relative Refractive Index

• Relative Refractive Index

• Quiz No. 8

• Quiz No. 9

• Real and Apparent Depth

• Quiz No. 10What is the refractive index of the pond water?

• World Above from a fishs eyes

• Total Internal Reflection

• Total Internal ReflectionWhen light ray hits the glass block at a certain angle of incidence, the eye cannot see the light ray.

• Total Internal Reflection

• Total Internal ReflectionThe maximum possible angle of refraction is 90-degrees.Total internal reflection (TIR) is the phenomenon which involves the reflection of all the incident light off the boundary. TIR only takes place when both of the following two conditions are met:

the light is in the more dense medium and approaching the less dense medium. the angle of incidence is greater than the so-called critical angle.

• Quiz No. 11For each combination of media, which light ray (A or B) will undergo total internal reflection if the incident angle is gradually increased?

• AnsPractice A: Light ray A is in the more dense medium and it will be the one which will undergo TIR.

Practice B: Light ray A is in the more dense medium and it will be the one which will undergo TIR.

• Critical Angle (c)

• Quiz No. 12Suppose that the angle of incidence of a laser beam in water and heading towards air is adjusted to 50-degrees.

Use Snell's law to calculate the angle of refraction?

• AnsGood luck!

This problem has no solution. The angle of incidence is greater than the critical angle, so TIR occurs. There is no angle of refraction.

• Quiz No. 13Some optical instruments, such as periscopes and binoculars use trigonal prisms instead of mirrors to reflect light around corners. Light typically enters perpendicular to the face of the prism, undergoes TIR off the opposite face and then exits out the third face. Why do you suppose the manufacturer prefers the use of prisms instead of mirrors?

• AnsA prism will allow light to undergo total internal reflection whereas a mirror allows light to both reflect and refract. So for a prism, 100 percent of the light is reflected. But for a mirror, only about 95 percent of the light is reflected. For these reasons, a prism will produce a brighter image due to the greater percent of light being reflected.

• Applications of T.I.ROptical fibresapplet

• Optical FiberUsed T.I.R to transmit light rays/informationTelephone signals, internet, cable television

• Rainbow Formation ACE (3 points)Homework groups of twoPresentation in classQuestions: What are the conditions for a rainbow to be formed?With the conditions existing, how does a rainbow forms?Why is the top of a rainbow always red and bottom violet?Extra Challenge:Make a rainbow, either in class or on video!

• Rare: Full-circle rainbow

• ***************************************************

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