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Visual Angle - PowerPoint PPT Presentation

Visual Angle. Darian S., Alyssa H., Caleb V.W., Jeremy K., Ly V., Joey C. Introduction. The size of the stimulus object and its distance are the most important Retinal size is measured in degrees of visual angle (360) Objects that you are perceiving are measured in many different ways Inches

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Visual Angle

Darian S., Alyssa H., Caleb V.W., Jeremy K., Ly V., Joey C.

• The size of the stimulus object and its distance are the most important

• Retinal size is measured in degrees of visual angle (360)

• Objects that you are perceiving are measured in many different ways

• Inches

• Miles

• meters

• Visual Angle = Object size/ Distance

• For any object:

• As it gets CLOSER to the viewer the visual angle INCREASES

• As it gets FURTHER from the viewer the visual angle DECREASES

• Objects that are different sizes can still have the same visual angle

• The Moon is 3,500km in diameter and is 380,000 km away from earth resulting in a 0.5 degree visual angle

• The Sun is 1, 400,000km in diameter and is 150,000,000km away. This also results in a 0.5 degree visual angle

• Visual Angle= Object size/Distance

• For example:the moon

Size/ Distance = 3,500/ 380,000= .5

• Visual Angle of the sun: .5

• The larger size perfectly compensates for the increase in distance from Earth

• How can the visual angle of two different objects be equal?

• Coffee mug (19cm), distance (90cm), visual angle (11.92)

• Phone (12cm), visual angle (11.92), distance: ?

Activity:

http://sites.sinauer.com/wolfe3e/chap3/visangleF.htm

• Look at the object on the next slide for 30 seconds

• Look at the following blank slide next

• Shift your vision to the blank wall closest to you

• What did you see?

• After you looked at the green dot a red afterimage should have appeared when you looked at the wall

• The green dot (now red) should appear smaller on the wall than the blank slide

• Why is this?

• After viewing the dot for 30 seconds the afterimages created are “bleached out” areas of your Retina

• This area doesn’t change in size as you change the distance of the object that you are looking at

• When the distance decreases, the visual angle remains the samewhile the image appears smaller