 # Real or Virtual? Real images A real image is one which can be produced on a screen and is formed by rays that converge. Imaginary images A virtual image.

## Presentation on theme: "Real or Virtual? Real images A real image is one which can be produced on a screen and is formed by rays that converge. Imaginary images A virtual image."— Presentation transcript:

Real or Virtual? Real images A real image is one which can be produced on a screen and is formed by rays that converge. Imaginary images A virtual image cannot be formed on a screen and is produced by rays which only seem to come from the image.

Lateral Inversion Image where left and right are swapped.

Upright Inverted

Reflection off a plain mirror

Image is: – Virtual. – Upright. – The same size as object. – Laterally inverted. Apparent distance from mirror to image is the same as the distance from the object to the mirror.

Reflection off a convex mirror F = virtual focal point

Reflection off a convex mirror Image is: – Virtual – Smaller than object – Upright

Reflection off a concave mirror F = real focal point

Reflection off a concave mirror Type of image formed depends on the distance of the object from the mirror.

Reflection off a concave mirror If object is between mirror and F image is: – Virtual – Upright – Larger

Reflection off a concave mirror If object is further than F from the mirror image is: – Real – Inverted – Laterally inverted – As the distance is increased the image size decreases. http://www.phys.ufl.edu/~phy3054/light/mirror /applets/cavemir/Welcome.html

Drawing a ray diagram for a concave mirror FF 1 2 Draw a ray that travels parallel to the axis towards the mirror and reflects through the focal point in front of the mirror. Draw a ray that travels through the focal point in front of the mirror and reflects parallel to the axis. Example 1

Drawing a ray diagram for a concave mirror FF 1 2 Draw a ray that travels parallel to the axis towards the mirror and reflects through the focal point in front of the mirror. Draw a ray that reflects off the centre of the mirror at the same angle it was incident. Example 2

Drawing a ray diagram for a convex mirror FF 1 2 Example 1 Draw a ray that travels parallel to the axis towards the mirror and reflects in a direction that makes it look like it originated at the focal point behind the mirror. Draw a ray that travels towards the focal point behind the mirror and reflects parallel to the axis.

Drawing a ray diagram for a convex mirror FF 1 2 Example 2 Draw a ray that travels parallel to the axis towards the mirror and reflects in a direction that makes it look like it originated at the focal point behind the mirror. Draw a ray that travels towards the focal point behind the mirror and reflects parallel to the axis.

Light through a concave lens

Light rays diverge. They appear to originate from a focal point in front of the lens. The image is: – Virtual – Upright

Light through a convex lens f = focal lengthF = focal pointC = optical centre

Light through a convex lens Light rays converge to focal point behind lens. Type of image formed depends on the distance of the object from the lens. http://www.phy.ntnu.e du.tw/ntnujava/index.p hp?topic=48 http://www.phy.ntnu.e du.tw/ntnujava/index.p hp?topic=48

Light through a convex lens If an object is further than 2F image is: – Real – Inverted – Smaller

Light through a convex lens If an object is at 2F image is: – Real – Inverted – Same size

Light through a convex lens If an object is between 2F and F image is: – Real – Inverted – Larger

Light through a convex lens If an object is between F and C image is: – Virtual – Erect – Larger

Drawing a ray diagram for a convex lens Draw: 1.A ray straight through the centre of the lens. 2.A ray that travels parallel to the axis towards the lens and refracts through the focal point behind the lens. 3.A ray through the focal point in front of the lens that refracts parallel to the axis.

Drawing a ray diagram for a convex lens FF 1 2 3 Example 1

Drawing a ray diagram for a convex lens FF 1 2 Example 2

Drawing a ray diagram for a concave lens Draw: 1.A ray straight through the centre of the lens. 2.A ray that travels parallel to the axis which refracts as if it came from the focal point in front of the lens. 3.A ray that travels towards the focal point behind the lens which refracts parallel to the axis.

Drawing a ray diagram for a concave lens FF 1 2 3 Example 1

Drawing a ray diagram for a concave lens F F 1 2 3 Example 2

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