Color. PHY205H1F Summer Physics of Everyday Life Class 10: Colour, Optics. Recall from Chapters 25 and 26

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$Sunsets Are Red Law of Reflection Virtual Image Formation Image Reversal Concave Mirrors Diffuse Reflection Refraction Total Internal$ Reflection Lenses Recall from Chapters 25 and 26 A changing electric field creates a field, which then changes in just the right way to

Reflection Lenses Recall from Chapters 25 and 26 A changing electric field creates a field, which then changes in just the right way to

E M Why Sunsets Are Red CHECK YOUR NEIGHBOR What property of a light wave mainly determines its colour?

1 PHY205H1F Summer Physics of Everyday Life Class 10: Colour, Optics Color in Our World Mixing Colored Light Why the Sky Is Blue Why Sunsets Are Red Law of Reflection Virtual Image Formation Image Reversal Concave Mirrors Diffuse Reflection Refraction Total Internal Reflection Lenses Recall from Chapters 25 and 26 A changing electric field creates a field, which then changes in just the right way to recreate the field, which then changes in just the right way to again recreate the field, and so on. This is an electromagnetic wave. E M Why Sunsets Are Red CHECK YOUR NEIGHBOR What property of a light wave mainly determines its colour? Color Color we see depends on frequency of light. 0.4 μm 0.7 μm A. Its frequency B. Its amplitude C. Its timbre D. A mix of all of the above High Frequency, Short f Low Frequency, Long λ 1

Selective Reflection Mixing Colored Light The spectrum of sunlight is a graph of brightness versus frequency. A red ball seen under white light.

Why Sunsets Are Red CHECK YOUR NEIGHBOR Rods and cones contain stacks of membranes. Rhodopsin is a transmembrane protein complex.

Opsin (protein component) Retinal (pigment) A. It will spread into a small range of colours. B. It will change to a single colour other than green. C. It will stay green.

2 Selective Reflection Mixing Colored Light The spectrum of sunlight is a graph of brightness versus frequency. A red ball seen under white light. Only is reflected, other colors are absorbed. A red ball seen under red light. A red ball seen under green light. There is no source of red light to reflect! Why Sunsets Are Red CHECK YOUR NEIGHBOR Rods and cones contain stacks of membranes. Rhodopsin is a transmembrane protein complex. A beam of white light, when shone through a prism, will end up many different colours. What will happen if a green laser is shone through a prism? Opsin (protein component) Retinal (pigment) A. It will spread into a small range of colours. B. It will change to a single colour other than green. C. It will stay green. Cone Rod 0.5 µm Light Light The retinal molecule inside rhodopsin changes shape when retinal absorbs light. cis conformation (inactive) Opsin Light Rhodopsin trans conformation (activated) Opsin Slide courtesy of Ross Koning, Biology Department, Eastern Connecticut State University 2

Response Curves for the three types of cones in the retina of the human eye.

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colcon.

3 Response Curves for the three types of cones in the retina of the human eye. Use both eyes, stare at area shown in blue for 15 seconds or so Slide from What do you see on this blank white slide? Blink if needed! Use Stare both at eyes, the bird s stare eye at the for 10 parrot s seconds eye without for 15 seconds tilting your or head. so This is called an after image Does it move around as you move your gaze? 3

4 Bird Was Red Use Stare both at eyes, the bird s stare eye at the for 10 parrot s seconds eye without for 15 seconds tilting your or head. so What colour is the afterimage bird? A. orange B. green C. blue D. yellow E. None of the above Bird Was Green Use Stare both at eyes, the bird s stare eye at the for 10 parrot s seconds eye without for 20 seconds tilting your or head. so What colour is the afterimage bird? A. red B. orange C. blue D. violet E. None of the above 4

Bird Was Blue Additive Primary Colours (light bulbs) and Subtractive Primary Colours (ink) What colour is the afterimage bird? A. red B. orange C. yellow D. green E.

5 Bird Was Blue Additive Primary Colours (light bulbs) and Subtractive Primary Colours (ink) What colour is the afterimage bird? A. red B. orange C. yellow D. green E. None of the above Discussion Question Why is this square red? A. The light bulbs in the projector emit light with blue frequencies B. The light bulbs in the projector emit light with green frequencies C. The light bulbs in the projector emit light with red frequencies D. Both A and B Discussion Question Why is the red folder in Harlow s hand red? A. The pigments in the paper absorb light with blue frequencies B. The pigments in the paper absorb light with green frequencies C. The pigments in the paper absorb light with red frequencies D. Both A and B 5

Discussion Question : Using the colour wheel.

in that region of your screen? A. Mainly yellow B. Blue and red C. Green and yellow D. Red and green .

. If an object is red, which of the coloured lights below would make the object appear not appear red?

6 Discussion Question : Using the colour wheel.. When the colour yellow is seen on the screen of your computer, what are the lights being activated in that region of your screen? A. Mainly yellow B. Blue and red C. Green and yellow D. Red and green Discussion Question : Using the colour wheel.. If an object is blue, which of the coloured lights below would make the object appear most black? Discussion Question : Using the colour wheel.. If an object is red, which of the coloured lights below would make the object appear not appear red? A. blue B. cyan C. yellow D. magenta A. red B. orange C. white D. cyan 6

Why the Sky Is Blue For small scattering particles, like nitrogen or oxygen molecules, frequency blue light is scattered much more readily than lower frequency red light.

7 Why the Sky Is Blue For small scattering particles, like nitrogen or oxygen molecules, frequency blue light is scattered much more readily than lower frequency red light. Why the Sky Is Blue frequency Why Sunsets Are Red CHECK YOUR NEIGHBOUR Doppler Shift for Light If molecules in the sky scattered orange light instead of blue light, the sky would be A. orange. B. yellow. C. green. D. blue. When a light source is moving from you, the spectrum is shifted toward the red. When a light source is moving you, the spectrum is shifted toward the blue. 7

Doppler Shift for Light Why Sunsets Are Red Light that is least scattered is light of low

The Doppler shift can be observed with carefully obtained spectra of very fast moving

YOUR NEIGHBOUR If molecules in the sky scattered orange light instead of blue light,

8 Doppler Shift for Light Why Sunsets Are Red Light that is least scattered is light of low frequencies, which best travel straight through air. The Doppler shift can be observed with carefully obtained spectra of very fast moving objects like stars There is a slight shift in absorption lines Why Sunsets Are Red CHECK YOUR NEIGHBOUR If molecules in the sky scattered orange light instead of blue light, sunsets would be Why Clouds Are White Clouds are clusters of various sizes of water droplets A. orange. B. yellow. C. green. D. blue. 8

Why Clouds Are White Size of clusters determines scattered cloud color. Tiny clusters produce bluish clouds. Slightly large clusters produce greenish clouds. Larger clusters produce reddish clouds.

e Red CHECK YOUR NEIGHBOR What does a white sky indicate? A. The atmosphere has mostly particles smaller than the wavelength of light B.

9 Why Clouds Are White Size of clusters determines scattered cloud color. Tiny clusters produce bluish clouds. Slightly large clusters produce greenish clouds. Larger clusters produce reddish clouds. Overall result is white clouds. Slightly larger clusters produce a deep gray. Still larger clusters produce raindrops. Why Sunsets Are Red CHECK YOUR NEIGHBOR What does a white sky indicate? A. The atmosphere has mostly particles smaller than the wavelength of light B. The atmosphere has mostly particles larger than the wavelength of light C. The atmosphere has a mixture of particle sizes D. The atmosphere has a lot of water vapour E. The atmosphere is filled with pollutants. Law of Reflection The angle of reflection equals the angle of incidence. Mirror B A A dentist uses a mirror to look at the back of a second molar (A). Next, she wishes to look at the back of a lateral incisor (B), which is 90 away. By what angle should she rotate her mirror? 2010 Pearson Education, Inc. A. 90 B. 45 C

Virtual Image Formation Two plane mirrors form a right angle.

3 D. 4 No light rays actually pass through or even near the image, so it is

Virtual Image Formation Alice looks at Bob s image a mirror and sees he has

Then she asks Bob to turn and face her, so she can compare the image to what

Bob takes a couple of steps forward, turns around and faces Alice.

10 Virtual Image Formation Two plane mirrors form a right angle. How many images of the ball can the observer see in the mirrors? A. 1 B. 2 C. 3 D. 4 No light rays actually pass through or even near the image, so it is virtual. Which picture is most likely a mirror image of Harlow? Virtual Image Formation Alice looks at Bob s image a mirror and sees he has a red shoe on the foot to Alice s left. Then she asks Bob to turn and face her, so she can compare the image to what Bob looks like in real life. Bob takes a couple of steps forward, turns around and faces Alice. Alice notes that the red shoe is now on the foot on the. Alice concludes: Mirrors reverse left and right, not up and down. Is this true? Can you see any flaws in Alice s reasoning? mirror real 10

Virtual Image Formation Bob in Mirror What really happens is

Bob chooses to rotate around a vertical axis, and therefore he

But if Bob wants to turn to face Alice, is there any other way

$Refraction When light bends in going obliquely from one medium$

11 Virtual Image Formation Bob in Mirror What really happens is the image is reversed front-to-back Bob turns to face Alice Bob chooses to rotate around a vertical axis, and therefore he looks flipped left-to-right. But if Bob wants to turn to face Alice, is there any other way to do it? Refraction When light bends in going obliquely from one medium to another, we call this process refraction. Cause of Refraction Bending of light when it passes from one medium to another Caused by change in of light 11

$Which might be the best path? C Refraction Light travels in glass than in air, so it minimizes the time it spends in the glass.$ Mud Dry Land 2 air water Dispersion Process of separation of light into colors arranged by frequency A fish swims below the surface of the water.

Mud Dry Land 2 air water Dispersion Process of separation of light into colors arranged by frequency A fish swims below the surface of the water.

12 1 Dry Land A B A soldier wants to get from point 1 to Point 2 in the shortest amount of time. Marching through mud is much slower than marching on dry land. Which might be the best path? C Refraction Light travels in glass than in air, so it minimizes the time it spends in the glass. Mud Dry Land 2 air water Dispersion Process of separation of light into colors arranged by frequency A fish swims below the surface of the water. An observer sees the fish at: A. a greater depth than it really is. B. its true depth. C. a smaller depth than it really is Pearson Education, Inc. Components of white light are dispersed in a prism (and in a diffraction grating). 12

13 Rainbows Rainbows are a result of dispersion by many drops. Dispersion of light by a single drop Rainbows Antisun Radius of circle is about 41 Doublerainbow The second rainbow has blue on the top, and a radius of about 53 Total Internal Reflection Total reflection of light traveling within a medium that strikes the boundary of another medium at an angle at, or greater than, the angle 13

Discussion Question An Optical Fibre Light waves with speed

14 Discussion Question An Optical Fibre Light waves with speed v 1 are incident upon the flat surface of a material in which they have speed v 2. For what condition is total internal reflection possible? A. v 2 > v 1 B. v 2 < v 1 C. v 2 = v 1 D. All of the above Speed of light in cladding is speed of light in core. than Medical Fibrescopes Converging Lens, f Videolaryngoscopy with a flexible fiberscope NOTE: Focal length is defined for initially parallel rays. Focal Point 14

15 Negative Diverging Lens, -f Diverging rays through a Converging Lens, f Virtual Focal Point Rays appear to emerge from Virtual Focal Point If an object emits rays at the focal point, they end up being parallel on the other side of the converging lens. f Real Image Formation, f image What will happen to the rays emerging to the right of the lens if the face is moved a little further away from the lens? A. They will remain parallel. B. They will diverge (spread out). C. They will converge (toward a focus). Light rays actually pass through the image, and a screen can be placed there, so it is real. 15

converging lens and the diverging lens. This is the end!!!! The final exam, will be: Wed. June 26 at 1:00pm sharp! (not 1:10!) Rooms TBA Test will begin promptly at 1:00 and will be 2 hours long.

16 The Camera A camera takes a picture by using a lens to form a real, inverted image on a light-sensitive detector in a light-tight box. We can model a combination lens as a single lens with an focal length (usually called simply the focal length ) A zoom lens changes the effective focal length by varying the spacing between the converging lens and the diverging lens. This is the end!!!! The final exam, will be: Wed. June 26 at 1:00pm sharp! (not 1:10!) Rooms TBA Test will begin promptly at 1:00 and will be 2 hours long. Please bring a calculator, and, if you wish, a lettersized aid sheet upon which you may write anything you wish This is the end!!!! Final Exam: First Page The final exam will cover the entire course, including all of the assigned reading plus tutorial materials and what was discussed in class. Approximately even spread over the course material 16

Please Fill Out the Online Survey For This Course!!!!!! Your feedback is vital to me. I promise I will read every word you type in the online evaluations.

17 Please Fill Out the Online Survey For This Course!!!!!! Your feedback is vital to me. I promise I will read every word you type in the online evaluations. The online system is open now (you should have received an already) The deadline is [ ] please don t forget!! Keep in Touch!! My office hours are Mondays and Wednesdays: 10-11AM, Fridays: 9-10AM. I am in MP121-B and my land-line is (please don t send text messages to my land-line) Please me ( jharlow@physics.utoronto.ca ) with any questions, or if you d like to make an appointment outside my office hours. 17

Selective Reflection

Selective Reflection PHY205H1F Summer Physics of Everyday Life Class 10: Colour, Optics Color in Our World Mixing Colored Light Why the Sky Is Blue Why Sunsets Are Red Law of Reflection Virtual Image Formation Image Reversal