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### Course: AP®︎/College Physics 2>Unit 5

Lesson 1: Reflection and mirrors

# Virtual image

Let's explore the concept of a virtual image. Created by Sal Khan.

## Want to join the conversation?

• wait.. why is reality a simulation in our brains
• oh i see,. perceived reality is such a strange concept but i get what your saying. does that mean that I could perceive to see a star millions of light years away and in my simulated reality it is visible but in actual fact it has died/exploded and disappeared by the time the light reaches me on earth
• Does anyone know how to calculate the minimum size of a mirror so that you can see your entire body?
• Not really 'half of your body' but 'half of your angular height', which depends on how far would the mirror be located apart from you (the farther away, the smaller mirror would do). Assuming the mirror is straight. Convex mirror could be even smaller and concave would need to be larger.
• At , why did you draw the incident ray at that angle? Can you draw it any way or direction you want? Do you randomly pick at what angle you want it to go?
• Yes, there will be light travelling in essentially all directions
• if there is no side behind the mirror then way rays passes the mirror ?
• They don't pass the mirror. Because of they way they reflect off of the surface of the mirror they look as if they come from a point behind the mirror, this is why it is called a virtual image it doesn't actually exist.
• Can someone explain the difference between real and virtual image clearly? What does it mean by 'a real image can be obtained on a screen ' ?
• if you look at the image in a concave lens. You will see it but you can not focus that image onto a screen. The light rays are diverging. They need to converge in order to be produced onto a screen

Actually, as you look such an image, your eye IS focusing the image onto your retina; which is a screen of sorts. The rays converge onto your retina
• What actually is a real image?
• A real image can be defined as the image produced by the reflection or refraction when the light rays arising from the object converge at a specific point.
• as an object is moved from a great distance to the focus of a spherical mirror the image moves away from the mirror.what kind of mirror is it-convex or concave
• why does a mirror flip left/right and not up/down
• A mirror doesn't flip left and right. What is on your right in the real world is on the same side in the mirror. Here is a good video on this: https://www.youtube.com/watch?v=vBpxhfBlVLU
• Real images (images on opposite side of an object) are always inverted. Virtual images (images on the same side of the object) are always erect/ upright
• You mixed up the sides. Real images (images on the same side of the object) are always inverted. Virtual images (images on opposite side of an object) are always erect/ upright.
• Whats the Focal point?
• The point at which light rays converge to (converging lens/concave mirror) or diverge from (diverging lens/convex mirror). In mirrors, the focal point is 1/2 the radius of curvature. You can also find the focal point by using the thin lens equation -> 1/f = 1/i + 1/o ; where f is the focal length, i is this distance from the lens to the image, and o is the distance from the lens to the object. Remember, this equation assumes a thin lens, a thick lens requires another equation that is more complicated.