# Homework Help: Virtual image,reflection?

1. Jun 3, 2012

1. The problem statement, all variables and given/known data
The diagram below shows rays come from object O are reflected by M1 and M2 in turn.Thus I2 can be seen by an eye.

2. Relevant equations
I am confused by I2,how does it form?
My book said that I2 is the image of I1
However,I1 is a virtual image,no light rays reach I1.
If there aren't any light rays,reflection can't occur.
So,how does I2 form?

3. The attempt at a solution
I have no idea :(

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2. Jun 3, 2012

### dipole

I2 is the image of I1. The image I1 is formed by the first mirror, the second mirror then "sees" O and I1, it doesn't distinguish between a virtual image or not, and so I2 is an image of I1, and I3 is a second image of O.

3. Jun 3, 2012

Reflection is the change in direction of a light ray at a boundary between two different media.
Light rays from an object are reflected to the original medium,a virtual image also formed.
However,I can't see any real light rays reach I2 from I1(suppose I1 is the object),why reflection still hold?

4. Jun 3, 2012

### dipole

Who said light rays have to reach an image? They only have to appear to converge there, if you trace them back through the mirror.

5. Jun 4, 2012

### ehild

There are no light rays from the virtual images, but rays emerging from the object do reach the eye. See the blue and green rays.

The human brain observes an object in the direction from where the light rays arrive to the eye. The ray "c" in the picture arrives from the direction where the virtual image I2 is. So a person "sees" the image of the object at I2.

You see we have some knowledge of Physics "burnt" into our brain. Here it is : "The light travels along a straight line." But the laws of reflection and refraction are not built in. You learn them in the school, but it is not an instinct. I think the fishing birds had to get the knowledge of Snell's law burnt in, to be able to catch a fish under water. A human baby learns that it have to reach the hand for a toy in the direction from where the light comes, as it is so in its environment.

ehild

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