PowerPoint on the physics of optical illusions and mirages

1. Optical illusions & mirages By Joloraine, Laura, Richele and Janelle

2. Is there actually water ahead? Is it actually moving?

3. Mirages What is a mirage? An optical phenomenon that creates the illusion of water. Where can one see a mirage? Commonly appears on days where the weather conditions are very sunny, hot and dry

4. How are mirages formed? Mirages are caused by light refraction Light bends when passing through different mediums. High temperatures on a hot summer day will heat the ground The ground warms the air that’s slightly just above it As light from the sun passes between these different temperature levels of air, it bends therefore creating a mirage.

5. Inferior mirages An inferior mirage is a mirage that appear to be below an object’s actual position. Light that would normally hit the ground, bends as it passes cooler, denser air to hotter, less dense air. Lower part of the light wave passes between the layers first. Some of the light are bent upward from their path and reach our eyes. Our brains automatically assume that the light is travelling in straight lines, so it seems like the image we see originated from the ground.

6. This happens, say when you’re driving on a hot sunny day seeing a car coming the opposite way. We see the image of the car twice. Light from the lower part of the car bends farther upward, so the mirage we see looks like a reflection of the actual object.

7. Superior mirages Superior mirages are mirages that appear to be above the object’s actual position. Occurs when the air near the ground is cooler than that higher up. Light waves will curve and bend downwards toward the colder air. We see a mirage of an object higher than it’s actual position.

8. Common mirage we see is a pool of water ahead. Light from the sky is refracted making it appear as if the sky is reflected by the road’s surface. We misinterpret that it’s a pool of water since our brain assumes that water also reflects the sky.

9. Optical illusions An optical illusion is a visually perceived image that is deceptive or misleading. We see color everywhere, but we don’t actually physically ‘see it’. We see the reflection of the light. Different wavelengths of light appear as different color.

10. How do we perceive optical illusions? The amount of light of an object determines how we see it. Brightly lit objects appear larger than a dimly lit object. The background of an object also affects how we see things. The use and arrangement of colour also has an affect on how we see things. Differences in shades of color give depth to flat surfaces. The eye and the brain work together to make us see the illusions. We can sometimes misinterpret the images due to different past experiences or psychological reasons.

11. Types of optical illusions There are 7 types Impossible optical illusions After-images illusions 3-Dimensional illusions Ambiguous illusions Distortion illusions Facial illusions Color and shadow illusions

12. Impossible optical illusions These illusions are classified as such due to the fact that we cannot justify what we see in the optical illusion.

13. After-images This type of illusion is where you look at an image for a period of time, then look away or look at an other type of image, causing you to see motion or color where there actually are none. Sometimes these illusions may cause you to see spots, or even a different image entirely.

14. 3-D illusions These types of illusions is where an image is portrayed in a way that make it seem to be a 3-D object.

15. Ambiguous illusions This type of illusion is where you have one complete image, but in actuality, there are 2 or more combined.

16. Distortion illusion This type of illusion makes an object look smaller, bigger, longer, shorter or be a different shape or color

17. Facial illusions These illusions show pictures of emotion. An image can be portrayed to be different things. Our mind can only interpret one image at a time, but in truth they are both there.

18. Color and shadow illusions These illusions are misleading because it depends on the way we see and compare things such as the contrast, colour, background.

19. Bibliography Gallant, Ray A. (1987) Rainbows, mirages, sundogs: The sky as source of wonder. London: Macmillan Publishing Wenzel, Angela (2001) Do you see what I See? The Art of illusion. London: Prestel Kirkland, Kyle (2004) Light and Optics. New York: Facts on File Simon, Seymour (1999) Now you see it, now you don’t. New York: Scholastic Inc. Seckel, Al (2006) Optical illusions: Science of visual perception. Canada: Firefly books Ltd Simon, Brandon. Seeing isn’t always believing. Retrieved April, 22nd, 2009 from http://library.thinkquest.org/J0110336/sitemap.htm Reference. Mirages. Retrieved from April, 24th, 2009 from http://www.absoluteastronomy.com/topics/Mirage Heidorn, Keith C. The Highway Mirage. Retrieved April, 24th, 2009 from http://www.suite101.com/article.cfm/science_sky/78177 Oak, Manali. How do Optical illusions work?. Retrieved April, 25th, 2009 from http://www.buzzle.com/articles/how-do-optical-illusions-work.html NSIDC. Superior Mirage. Retrieved April, 26th, 2009 from http://nsidc.org/arcticmet/basics/phenomena/superior_mirage.html